So the folks at The Hollywood Temp Diaries are here to help you (see Part 1 and Part 2 for previous examples) and clue you into the popular vernacular in this town.
Avail (as in, "When is her next avail?") -- The truncated version of "availability." I'd write something clever here, but I'm busy now. Let me check my avails to do this later. Uh oh. I just did it, didn't I?
THX - Strangely this Hollywood term has nothing to do George Lucas' company or that earsplitting noise you'll hear at the multiplex. This is simply assistant speak for "thanks," which is the informal version of "thank you" (abbreviated "TY"). How is it that the abbreviation of the shortened version is actually longer than the abbreviation of the longer version?
Have (frequently used in, "I don't have this person") -- No one in Hollywood actually owns anything. Their BMW X5 - leased. Their idea for the next great movie - owned by the studio that made it the first time. Their date to the Benjamin Button premiere - an escort. So when an assistant says they "don't have" their boss, they simply mean this Hollywood exec is busy doing something way more important and is unavailable to speak to you. Such activities may include playing Guitar Hero, doing cocaine or flirting shamelessly with a client.
The Blacklist - One assistant famously thought this was a throwback to the House Committee on Un-American Activities. Actually it's just a just a list of the "best" unsigned movies, all of which will eventually be directed by Jason Reitman.
In the Canyon (used in, "I can't hear you, I'm in the Canyon") -- Your boss's iPhone can do everything from taking pictures, to playing music, to recommending which 5-star sushi restaurant they should expense today. The one thing it can't do is get good reception, especially when taking Laurel Canyon or Coldwater Canyon. This is also a Hollywood exec's best excuse for getting off the line with an agent by faking being "In the Canyon."