Often refers to "Jack-off instruction" or "Jerk-off instruction" Involves a girl or a guy "instructing" the audience how and when to stroke and how/when to ejaculate while often teasing or performing other sexual acts. It's mostly mixed with cosplay and other fetishes like foot worship, femdom and BDSM.
Saul: Holy shit dude, I've just busted the biggest load on some shit called JOI, you know of it?
George: Yeah, bro. My older sister used to film JOI when parents kicked her out
by EmporioF October 17, 2019
Giving someone instruction on how to jerk off, and or masturbate for pleasure. JOI=jerk off instructions.
Sally gave her boyfriend JOI over the phone during phone sex
by KatieValdez September 6, 2018
Acronym for Jerk Off Instructions. A POV porn niche where the porn girls give explicit and detailed instructions on how to jerk off.
Greg found out that he couldn't stroke to a fulfilling orgasm unless he was watching hot girls in JOI porn.
by sarasplayroom.com August 31, 2010
Jerk off instruction

A category of a pornographic video featuring a woman giving instructions to someone on how to masturbate.
Yesterday I came to JOI and it was so amazing.
by pzeudonym1 February 10, 2021
Japanese Olympiad in Informatics
I searched up a JOI problem and got pornhub links instead
by ur mom gay234 March 20, 2020
:Person 1: You wanna do JOI?
:Person 2: Sure, tell me what to do.
by Pluusja April 29, 2018
Jerk Off Instructions. A millennial phenomenon, wherein a selfish generation managed to become even shittier at sex by demanding female partners (mostly paid, always bored) instruct them on how to handle their own feckless anatomy. Nevermind that having been born with a vagina offers limited insight into male self pleasure. And so she performs a kind of thankless one woman show, cheerleading a monosyllabic goon to orgasm.
Sex Worker #1: Can you believe this fucking ding dong requested JOI again?

Sex Worker #2: If I see one more Pro-Domme advertising JOI, I’ll scream. It’s not femdom, it’s emotional labor!
by LydiaFaithfull April 11, 2020