How outrageous (or inappropriate) this game gets is entirely dependent on who you're playing with.
The words on the cards are all real, and all of them have legitimate definitions. Words like bloviate, canoodle, collywobbles, wabbit, smellfungus, and hoosegow are all in the dictionary (at least, the good dictionaries have them. Yes, even wabbit and hoosegow. Balderdash has hundreds such words--the goal is to provide definitions for each of them.
Play goes down like this. When it's your turn, you draw a card. On one side are five words that appear to be in an alien dialect, and on the other are definitions of each word. These are all words in the English language. You'll pick one, read it out loud, and secretly write the real definition on a piece of paper. Everyone else writes whatever they feel like. Then you read everyone's definitions, and they vote on the one they think is the correct definition. Points are scored for guessing the correct answer or having your answer chosen by another player.
A boffo variation allows players to simply vote on their favorite definitions. Points are immaterial in this version.
Balderdash is (or ought to be) every English major's favorite game. I know a few English professors who put Balderdash higher on their list of favorite things than some of the great classics of Western literature.
Many of the words are sesquipedal. Oftentimes, proffered definitions bring to light players' mumpsimuses, and then everyone can chaff them for being cockeyed and deranged. 'Tis great fun.
The best fun, in fact. I played a game of Balderdash once that got so out of hand I ended up sick from laughing. Literally, physically ill. I'll spare you the particulars, but let that be a remonstrance to buy this game at once and play it with the funniest people you know. You'll not be disappointed.