J :

Masturbate, stroke your own cock with your hands.

Cum, ejaculate.

A guy you regularly jack off with.

An athletic, muscular or well-built guy, or short for jockstrap.

A covering for the cock and balls, has two leg straps and leaves the butt exposed.

K :

Sexual preferences or behaviours that are considered to be 'out of the ordinary.'

L :

Long-term relationship.

Fetish wear including chaps, harnesses, and boots.
The men that wear such clothes.

A drug prescribed for erectile dysfunction, sometimes taken by gay men to improve and pro-long erections during sexual encounters.

Sex drive; eg, he had a very high libido.

Cum, ejaculate.

A liquid applied to the cock and ass before anal or other sex to reduce friction and make penetration easier, safer and more comfortable.

Fucking someone in the ass while getting fucked in the ass at the same time. Lucky Pierre is the guy in the middle of a three-way.

M :

Male to Male, Male for Male.

Mate, buddy, friend, often sexual.

Married man.

Mutual Oral, when two partners provide oral to each other not necessarily at the exact same time.

The sexual enjoyment of pain, torture, abuse etc.

Someone who provides massage services for a fee, may or may not include erotic services.

Jerk off, stimulate the penis with your hands.

Penis; eg: Beat your meat.
  Man flesh; eg: He is a great piece of meat.

Sex between three people.

Jerking/fucking a guy until he squirts every last drop of cum, can include the forced ejaculation caused by stimulating the prostate.

When on partner lays on his back and the other lies faces down on top of him to fuck. A very awkward position for butt-fucking, requiring agility and a long dick.

Cum shot, generally a porn term, the scene where the porn star shoots his load is referred to as the "money shot."

A jock/built guy who likes to take it up the ass.

When two (or more) guys jerk each other off.