AD - short for ADVERTISEMENT. Note that there is only one 'D' in both the short and long versions of the word.
I realize that this is neither a code word nor an acronym, but it is so often misspelled as "ADD," that I wanted to add it in here.
It is what it sounds like: provider ‘cleans’ your body with her tongue. Not just a lick here or there or extensive use of her tongue, but a full-body, thorough experience. YMMV, but holy hell was it awesome.
It’s kind of self-explanatory, but it showed up in a few reviews and was new to me. I’m leaving this here because until I got one I wasn’t sure if I guessed right.