When a player scores three goals in one soccer or hockey game.
Yesterday, my nephew had a hat trick in his hockey game!
Have a bee in your bonnet:
To talk about something you think is important.
She has a bee in her bonnet about climate change. Don't bring it up during conversation because she won't stop talking about it once she starts!
Head Over Heels:
Overly excited, especially related to liking or loving someone.
He was head over heels for her after their first date!
Hit the Books:
I guess I need to hit the books tonight, or else I’ll fail!
Hit the Hay (Hit the Sack):
Go to sleep.
I’m gonna hit the hay; it’s getting late.
Hold Your Horses:
You need to be patient.
Hold your horses. I’m almost ready to leave.