Jamaican patios; slang meaning "of course" or "I know"

forsure, agreein wit sumtin.

Slurry way of saying "don't know". People either say it like that when they're feeling to lazy to speak properly or don't want to speak at all.
Another reason is because they think it's cool to use slang and miss-pronounce everything.

When you rub someone’s nipples on an escalator without warning

fuh sure, zeen