"Did you hear about Mr. H, the rapist social studies teacher? I heard he crumbled like 2 squillion kids' biscuits!"
The disappointing act of giving up on one's intentions, usually at the very last minute. This usually involves peer pressure or just a total lack of backbone.
Adjective - to describe a person who is likely to crumble often. e.g. 'That guy is a right crumble'.
Sometimes this adjective becomes a nickname as such, but this is only ever used when someone is a notorious crumble.
Nick: "You coming out in 2 weeks, Don?"
Rose: "Yeah, sure"
*2 minutes to night out*
Nick: "What time do you wanna head off, Don?"
Rose: "Not going, sorry......"
----- (This can work the opposite way round too) ------
Juan: "Nock, I thought you weren't coming out tonight? You said "I can't come out tonight, I'm trying to be healthy and don't want to feel rough tomorrow", but you're here!?"
Juan: "Mate, you propa crumbled!"
Girl 2: Yeah but it was obviously the guys first time in a while
Girl1: Why, did he crumble?
Girl 2: He crumbled the whole time!