According to Coach Jason Brown from Netflix's Last Chance U - A person who does dumb shit and knows better, but simply cannot help him/herself. Someone who does dumb shit continuously, in a non-malicious manner.
Trent Richardson is a slapdick for allowing his friends and family to have account to his bank account . He is also a slapdick for ignoring his bank account for 10 months while his friends and family withdrew $1.6 million.
A "slapdick" is simply that guy or that girl, who thinks he/she is all that. Some dude walks in a party with a fake tan, popped collar and acts like they know everything about everything, yet not one person there cares what they have to say, gives them attention or wants them there.
game played for fun by homosexual or heterosexual males. Game usually begins by slapping the other players dick when they least expect it. Famous moves include grab and roll or pinch and twist.