Turn off
Basically something that disgusts you, find embarrassing or unappealing (mostly) about the opposite sex.
1. Lisa: "So, my boyfriend and I had sex for the first time last night."

Natalie: "Really!? Oh my god, how was it?"

Lisa: "It was okay... but when he started climaxing, he farted! It smelled so bad!"

Natalie: "Ew!! What a turn off!"

2. "There was this random girl who danced with me at the party last night. She was so hot. But when she grinned at me at me, I noticed she was missing two front teeth. Immediately turned me off, man."