Butthook, or Hook For Short is a Synonym to Butthead, Butthole, etc. Also can mean someone who is lazy. Bum

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

When you stick your finger up your butt and you get shit on it and then you stick that finger in your friend's mouth and pull really hard.

An attachment to the stock of a rifle or shotgun, often used in competition, which is tucked under the shooter's arm thereby counteracting the tendency of the weapon's muzzle to droop, or to allow one-handed firing.

1.
Known as a synonym to butthead, or bum. Short Form known as simply "hook".

a real jerk

A specific instance of a doohickey, considered to be the ultimate "useless thing".