expression, godan verb (-ru)
be hanged; be struck dead; eat one's hat
Figurative expression used to stake one's life on a claim, similar to 'I'll eat my hat if I'm wrong.' Often used in conditional or emphatic statements.
もし彼が遅刻したら、首をやるよ。
If he's late, I'll eat my hat.
あのチームが優勝するなんて、首をやってもいい。
I'd stake my life that team won't win the championship.