Below are some good bridal words to know prior to trying on wedding gowns. Your version of what you think a “mermaid” is may be totally different than your consultants. If you have a good understanding of these words, you’ll be able to better articulate what you want and don’t want.

Open Cup: Sample gowns come with typically a “B cup” in them to try on. If you’re something larger such as the very common Double D, then if a consultant mentions you need to “open the cup” it is so you’ll sit in to the bust deeper as opposed to be smashed as you’re trying on. This usually requires an extra charge but is usually worth every penny. You’ll be able to see that better as you try on. It is particularly important in sheer gowns where the bra cup kind of shows. Opening the cup can prevent from exposing side boob or under boob.
Silhouette: The line of a dress, or the garment's overall shape. Silhouettes can be used to emphasize and alter a bride's shape to create a flattering illusion. Different bridal dress silhouettes are designed to flatter different body types. Understanding different silhouettes can help you find the most flattering one for your body type. For example, the most common are: Ball gown, fit & flare, mermaid, A-line, column, and sheath. 
Neck line: The shape made by the edge of a dress at the front of the neck or on the chest. Common necklines are: Sweetheart, “V,” halter, square, portrait, boat, straight-across.
Hollow to hem: is the length from the depression or indentation at the base of the front of your neck to the edge of the hem on the dress. This is best done with dresses that have a very intricate pattern as the bottom. The hollow to hem should be done while wearing the potential heel height. This customization typically costs extra. It is best to weigh the pros and cons of hemming vs hollow to hem.
Illusion: Sheer netting-type material that forms a see-through layer yet offers ‘the illusion’ of coverage. Sometimes this is also done on a sleeve with appliqué. Or it can be seen on a back with buttons.
Trunk show: a special event in which a bridal salon features a particular designer's collection. The bride has a unique opportunity to view and try on wedding dresses straight off the runway before they are available in stores as well as styles from previous seasons. Typically, a rep from the brand or the designer themselves will come offering addition add-in’s/customizations sometimes. 
Sample: A sample is the bridal store’s piece to be tried on and to be ordered based off of. Where you can order in typically different colors and the size that your measurements place you in. Samples have been tried on by many people so if you can afford to order new, do! If you find a gem of an off-the-rack sample, then great! What a steal. 
Horsehair trim : Flexible polyester mesh designed to reinforce and define both straight and curved hems, transforming a limp skirt edge into one with flair and strength.
Appliqué: Fabric or lace cut-outs affixed to the gown, train or veil.
Ball gown: It is fitted in the chest and flares at the waist into a very full, often multilayered, skirt. This is the fullest of silhouettes and the most “fairy-tale” or “princess-like.” This style is flattering on almost any body type.
Mermaid: The mermaid silhouette is designed for women who have curves that they want to accentuate. It is fitted through the chest and torso to the knee, at which point it flares out dramatically at the “break,” or line across the knee area. 
A-line: This gown silhouette tends to work well for everybody type. It is similar to the ball gown, with a fitted chest and torso, however, the skirt is less full and dramatic, it usually has less crinoline. The slight flare creates a flowing line from the torso to the floor, or an overall body shape like the letter A.
Column: A fitted bodice to a narrow, tailored look over the waist and hips, and straight to the floor. No flares, no poofs, and not as fitted as a sheath. 
Sheath: The sheath silhouette is used to refer to dresses that are form-fitting from the bust through the length of the thighs. 
Blusher: This is the single layer that is worn over the face during the ceremony, and then flipped back over the head after the ceremony. It can be worn alone and then removed after the ceremony or paired as a layer to a longer veil. Blushers are traditional, not a must, just a preference. Dresses that have them built in can also be worn with them kept back the whole time.
Cathedral: The most formal style of veil, cathedral is usually paired with a cathedral-length train. This is the best style in my eyes for photos and continuity of the look. It is seamless. Short veils usually distract from the bride because it creates a break. Stylists use the word ‘regal’ to describe this veil.
Waltz: Reaches from the comb to the hem of your dress. It is easy to wear and can be kept on the whole night if you shall please.
Fingertip: This veil extends down to your fingertips when your arms are hanging straight. This is the most versatile and most popular veil length for its ease of mobility, low cost, and functionality.
Bustle: Gathering the train up to attach securely via clips, hooks, or buttons at the back of the dress, to present an attractive gathered effect above the gown’s skirt so one can dance and move around at the reception. The French bustle goes under the gown and the American goes on top of the back of the gown.
Crinoline: The layers of tulle or netting worn under the gown’s top layers to add extra volume to a full skirt. Crinoline may be attached to the dress or added as a separate undergarment. Layers can also be removed in alterations to take a ballgown to more of an A-line. 
Lining: this covers the inside surface of the dress. When trying on, some dresses may be sheer but you can “line” them for an additional fee. This gives more coverage, structure, and support. Lining colors typically change when changing the color of a gown on an order. 
Tailoring/Alterations: Fitting your gown to you! No one is a perfect 4 bust, 4 waist, 4 hips. That just doesn’t look amazing either. We are women with usually an hourglass figure. Meaning we have to order a size based off the largest part of our body affecting the silhouette of the gown. Thus, requiring tailoring or alteration to mold the gown to fit your exact measurements. Alterations also include hems, bustles, taking in the gown/letting out, taking up the straps to provide support, etc. These costs aren’t included in the cost of the gown.
Shorten the waist: If you are short waisted then some bodices may look too long on you, not fully showcasing the small waist. Some dresses can be ordered with a shorter waist, so it hits in the correct spot. This is an additional charge. 

After reading, you are now stepping ahead of the average bride and you will be able to best describe what you like and don't like to your consultant. This will make wedding dress shopping much more of a breeze. Remember, the perk to having a stylist is their ability to articulate your vision to your bridal consultant. If you don’t want to learn the lingo-grab a stylist!