Spanish word for flipflop/sandal/slipper. It's what Hispanic/Latino parents (usually mothers) use to beat their child's ass when they've had it with their misbehaviour.
And don't even try to run, they can throw that thing round a corner like boomerang and if you manage to run out the house then don't expect to be allowed back inside without getting twice the original punishment.
Hispanic/Latinamother: *child's name*, GET OVER HERE NOW.
Kid: Shit, I can already feel la chancla getting spanked round my ass.
When Dionne Warwick was messed up on heroin in the early 1970s and a critic blasted her bizarre concert performance, she phoned the guy and screamed at him: "Yo mama suck canal water!"