A turd so large that it contacts the bottom of the U-bend while still emerging from the unfortunate crapper's anus, causing him/her to be literally jacked up off the seat. There is a particular risk of manjack when using toilets of the curious German or Austrian design, which have the U-bend at the very front of the pan and a shallow "deck" for inspection of stools.
Three or more dudes spooning with boners.
Three or more dudes have anal sex in bananna formation.
Three or more dudes with there boners cupping each others asshole.
Derived from the video game "Half Life 2" a "manhack" is a small flying drone armed with three sharp blades that would chase the main character, Gordon Freeman, around during the early levels of the game. This term has been adapted in recent years to describe any AI or remote controlled roto-craft such as helicopter or quadrocopter that is out of human control.
::Two guys in a field::
Guy 1 : So I just got the new firmware uploaded to my co-pilot chip lets try it out.
Guy 2 : Shouldn't you test that out with the engine control unitunplugged?
Guy 1: Fuck you guy.
::1 minute later ::