A hand job that is given to a guy while wearing pants, preferably sweatpants. Acronym for "over the pants job".
Brian: Dude, how's it going with Jenna?
Chris: It's OK, I've only gotten an OTPJ so far...
Brian: ONLY??? I live for OTPJ's.
Chris: Actually, now that you mention it, it was great. I was wearing sweatpants, so it felt extra good.