refers to an individual, usually male, who has done something reminiscent of the suburban cult legend of belasco. usually used to characterize someone who has sustained a sport injury and will not seek medical attention and/or has alot of sex but is afraid to film it.
Could also refer to someone who is a "bro" and likes the comic book character belasco. this is used sarcastically.
Look at that limp, Kevin is being a real Belascbro