The old men that you see in the locker room who'd never workout, but stays in the steamroom, sauna, and showers until they look like a raisin trying to get their peeps at you!
To Gump is to play ping pong such as Forrest Gump did. It's an easier way to ask someone if they want to play ping pong with you, without sounding like a fruit.
"Hey man, you want to Gump"
"I'm not really sure, I'm hammered drunk and won't be able to hit the ball."