The art of appearing to be productive at work without actually doing anything of any value. In its truest form this involves loud, screeching equipment, foul language, and blaming everyone/everything around the half-asser in a covert manner, i.e. running to the head boss and ratting on everyone else while simultaneously kissing the head boss' ass.
Employee 1: Damn that Rocky! He's such a pussy!
Employee 2: Nah man, that n#%&a's perfected the art of half-assmanship.
1: The ability to navigate difficult situations by means of one's enormous balls.
Origin: Something between sportsmanship, craftmanship, and balls. Possibly boats, too.
Jeff, in an act of superb ballsmanship, used the public address system to win the penis game in a public library.