otp abbreviation for "on the piss". Drinking term.
I'm gonna get otp tonight, u keen?
Means "over the phone" a lot of guys use it when trying to get girls to send pictures of themselves over Snapchat or text
Guy: hey can we do stuff otp?
Girl: sure wait until I get home.
OTP despite common misconception usually means On The Phone when texting.
Me and Jenny were talking OTP last night.