A jack shack is a place like a seedy massage parlor or "modeling studio" or "gentlemen's spa" where you can get a hand job for a reasonable price, and little fear of getting arrested for soliciting.

Invented in Borat's movie. It is said, when something great happens.

Usually specific to soldiers, or other people who are forced to live in close proximity for long periods of time without either sexual activity or privacy, a jack shack is a small shack made out of blankets, ponchos or poncho liners that is erected so that the builder can masturbate in relative peace. It is often explained away as a means to block light, or provide privacy to change, despite being erected almost exclusively around one's sleeping quarters.
syn: whackatorium

An establishment that provides cost effective massage treatments of the sexual variety. Also known as a massage parlor.

A shed, shack, camping shelter, tent or other shelter which provides protection from view and privacy, when used by the inhabitant (often a teenager) to masturbate, smoke marijuana, or drink alcohol without being discovered or disturbed.

When a inmate put his sheets around the bottom bunk to make a shack to Jack off in

A building which sells sex toys and porn videos and has 25 cent peep shows in the back room.