1. Slang term that is most likely to have originated from Britain meaning to make out
or have casual sex
2. To masturbate or have an orgasm.
If someone is able to 'get off' to something, they find it sexually arousing
3. To enjoy something, most often used to express the 'high' attained by the use of drugs or else sexual relief.
1. "Jason got off with Jackie at that party last night- did you hear?"
"Wow really?! I am shocked! Shocked, I say!"
2. a) "Gee, I could really get off to some gay porn right now."
b) "I get off fourteen times a day!"
3. "I'm not really into drugs, but sometimes I get off to weed."