So you've found yourself in this strange new world called the Brazilian jiu jitsu community, surrounded by sweaty people wearing pajamas, "oss"ing and bowing to each other, and speaking something that sounds like English.
Welcome. Now here are a few commonly-used words and phrases that you might find helpful as you begin to learn "jiujitsuese":
Pronounced "oh-sss", with as long an "s" sound as your little heart desires. This is one of the most versatile words in the jiu jitsu community. It can be used in greeting, in place of "thank you", as acknowledgement of a higher belt's mad skills, or as a general affirmation of solidarity with your fellow jiu jitsu practitioner.
Pronounced "ghee", with a hard "g" (like in grapefruit). This is that funny looking pajama set you wear to train in. Yes, it is a kimono, but if you call it that, you'll single yourself out as a serious newbie.
Somewhat interchangeable with "fight", "train" and "match", usually in reference to the actual live-sparring rounds with your fellow teammates. Can be used as a verb: for example, a higher belt will ask you "Want to roll?" before she proceeds to "roll" you into a little pretzel. Or it can be used as a noun: "We had a great roll, before he decided to hulk out on me."
Learn to love this word, or find yourself visiting the emergency room... often. The "tap" is the physical or verbal resignation of defeat in a jiu jitsu match. It typically comes before the point of pain - as with an arm or leg lock - or passing out - as with a choke. It was also once used in the name of a really tacky clothing brand.
The part of training that consists of many, many... many repetitions of various techniques. It's not the funnest part of jiu jitsu, but it is an indispensable aspect of one's training regime. It is based on the idea of muscle memory; do something often enough, and it takes less conscious effort to do it in the future.
A training method in which a single person stays in the middle during a period of time while two or more opponents spell each other out against him/her. Depending on the intensity, this can also be known, lovingly, as a "shark tank". Because the person in the middle continually faces a fresh opponent, it gives him/her a much more intense training than a normal roll.
Now that you're armed with some lingo, go forth, grasshopper, and make us proud.