Be off like a prom dress (in May) American simile humourous
To leave somewhere quickly and suddenly
Why was you off like a prom dress in May at last night's party?
She was off like a prom dress in May after she received a call.
To seduce and make someone think you're in love with them (the fact is that you're not) then leave them
To flee or run
To flee overnight, often to avoid creditors
To leave a place, especially to start a journey
I'm leaving
The verb" be" must be conjugated according to its tense.
This simile puns on two senses of off, with the idea that a prom couple is likely to have sex.