What it means
A sook is someone who's having a sulk, a whinge, or acting a bit overly hurt when everyone else reckons it's not that deep. In Aussie and Kiwi English it's a pretty standard dig for someone being soft, precious, or too easily rattled. Not a full nuclear insult, more a cheeky shove to harden up a touch. You also hear sooky and sooky la la when people want to ham it up a bit more.
Usage examples
"Oi, you got a bit of rain on you and now you're moaning. Chuck on a jacket, mate, and stop being a sook."
"Tim spent forty minutes sulking because the BBQ ran out of snags before his turn, what a sook, the cricket was still on and the rest of us were happy with bread and onions."
"My boy turned proper sook when the ute got a flat tyre and we missed the start of the footy, twelve years old, arms folded, headphones in, full Olympic-level pouting from the back seat."
"Don't be a sook, it's only a bit of banter, nobody nicked your lunch."
"He copped one spray from the coach and went full sook on the bench for the whole second half."
Where it comes from
Sook goes back to an older Scots and dialect word for a suckling calf or young animal still feeding from its mother. That soft, dependent image stuck around and in Australian and New Zealand English it drifted into the slang sense of someone seen as whiny, oversensitive, or a bit emotionally flimsy.
Other ways to say it
This expression also appears in