Jack Off / Jacking Off
Slang for masturbation, usually referring to a male.

Jack Shack

Refers to an establishment (massage parlor, lingerie modeling) that is not usually full service; expect only massage (usually nude or topless) and handjob, but more services might be available.
Jail Bait
Slang for a sexual partner who is under the legal age of consent.
Jelly
A material used to make sex toys, specifically vibrators and dildos. Jelly sex toys are usually brightly colored and soft and squishy to the touch.
Jelly Dildo
A dildo or dong made of jelly.
Jelly Vibrator
A vibrator either covered in or constructed out of jelly. Most jelly vibrators are completely coated and "sealed" within the jelly.
Jelly Toy
Slang for dildo.

Jewels
Slang for the scrotum.

Jill Off
Slang for female masturbation.

Jimmy Hat

A condom

Jism
Slang for semen.
Jizz
Slang for semen.
John
Slang for a man who engages in sexual activity with a prostitute.
Johnson
Slang for the penis.
Joint
Slang for the penis.
Joy Jelly
Slang for sexual lubrication.
Joy Juice
Slang for the natural vaginal lubrication produced by a sexually aroused female.
Jugs
Slang for breasts.
Juice
Slang for the natural vaginal lubrication produced by a sexually aroused female.)