In short, when someone lies their intention to call back or otherwise re-contact someone else.
(By the way, the Hollywood Blowoff can be easily avoided simply by using the honest phrase: "Sorry, I don't give my number out", or "I'd prefer to contact you if I'm interested")
AVERAGE ALVIN: May I have your telephone number?
-or- "Can I call you"
-or- "Do you have a card?"
-or- "When will it be ready"
-or- "When will I know the results of the audition?" etc.
SNOTTY AGNES: Don't worry darling, I have your card (when, in fact, Average Al either has no card or never gave it to Agnes).... I'll call you... Honest.
-or- "I/We have your number"
-or- "You'll be hearing from us/me"
-or "I'll/We'll let you know as soon as I/we find out"
AVERAGE ALVIN: Why Agnes, you hideous, loathesome, stinking bitch from hell....You're giving me the Hollywood Blowoff, AREN'T you?! Jeez, I'm SO sorry I came to this book signing and wasted both my time and money on you.. Here, please keep your sorry little book and read it.. That way you'll have a better idea of yourself than I now do, you pitiful, pathetic asshole, you. If you ever, ever walk through MY neighborhood. you'd better look both ways before crossing!