(verb) To take a slightly unattractive girl to a sleazy pizza place after drinking heavily, not order any pizza, but instead make out with the girl in the corner while shitty music plays and the counter-attendants look on unhappily. One who jumbo slices will not take the girl home after.
Mikey's hitting on every girl at the bar tonight. He must really be trying to jumbo slice!
The HUGE display screen typically found at sporting events. It shows game/player stats, scores, replays, advertisements, etc to the crowd.
Jumbotron is actually a Sony trademark name, but the word is used to refer generically to any gigantastic LED screens like it.
At a basketball court, the jumbotron might be about 11 feet wide, but in a football stadium, it'll probably be more like 33 feet.