Tush (noun)

1. The buttocks; the backside; the rear end.
2. Derogatory term used to refer to the buttocks.

Origin:

Early 20th century: origin uncertain, perhaps from yiddish tush, tuches, or russian tush "rump".

Examples:

1. She smacked him on the tush playfully.
2. He was a firm believer in the power of a good tush workout.
3. The tush was sore after sitting on the hard bench for too long.
4. He gave her a playful pat on the tush.
5. It was not appropriate to use the word "tush" in a formal setting.