as said by Tyler Durden. one willing or set out to sacrafice themself for the greater good.

Consider the first monkeys shot into space. Without pain, without sacrifice, we are nothing.

Space Monkey is a game that teens play where a person either chokes his/herself or has someone else do it until they almost pass out. It can cause brain damage due to lack of oxygen to the brain.

a game in which the main objective is to make the other person pass out, for fun.
to play this, the person who wishes to pass out breaths into a sweatshirt or something else for 20-30 seconds to make them slightly oxygen deprived. They then hold their breath while the other player pushes their stomach hard until the oxygen deprivation causes them to pass out.
Do not attempt this without someone willing to catch you as you fall to the ground due to fainting.

A song by Placebo, track 4 on the album "Meds."

A game played by boys and girls ages 10-20 who can't manage to get their hands on any weed. Choking yourself causes lack of oxygen to the brain and can cause oneself to lose consciousness or die. Kids think that it makes them feel high, while really it just destroy's their brain.

Spacemonkey is the nickname of Daniel Jackson, given by Jack O'Neill. Daniel hates said name, which makes Jack use it even more. Given to him after he is alive after all (he almost pulled a Daniel Jackson).