What it means
To go spare means to suddenly lose your temper and kick off way harder than the situation probably deserves. It's very British and usually lands in those last-straw moments when somebody's patience snaps and they start stomping, ranting, and having a proper little eruption over it.
Usage examples
"Dad went spare when he clocked I'd fixed the telly using the remote and a butter knife. Now he's marching about, muttering, like it's EastEnders."
"Mum went spare when she saw the muddy footprints all the way up the new stair carpet."
"He'll go spare if he finds out you borrowed the car without asking, best fill the tank first."
"She went spare when someone binned the leftovers she'd been thinking about all day."
"Don't tell Nan you scratched the table or she'll go spare before you've even sat down."
