What it means
It means basically no chance at all, and you usually say it with that dry little sarcastic snap, same lane as yeah, right. You throw it out when someone’s hopeful about something that is clearly never happening. The joke is that fat sounds big and promising, but the whole thing means the exact opposite.
Usage examples
"You reckon the boss will sign off overtime? Fat chance. They’ve already binned the good teabags and put a padlock on the biscuit tin."
"Fat chance of getting a seat on the train at rush hour."
"He thinks they will apologise? Fat chance."
"You think landlord’s giving the deposit back without a fight? Fat chance."
"Fat chance I’m getting through customer service before lunch."
Where it comes from
Recorded in English by the late 19th century, this phrase runs on pure irony. Fat should mean big, juicy, loads of it, but fat chance lands with the exact opposite meaning: almost none, basically forget it. That sarcastic flip is the whole trick, and it’s stayed sharp ever since.
