When you or someone are bumming are bumming so bad (for drugs, money, pussy, etc.), that you begin to act completely inappropriate, making horrendous decisions, and likely saying some of the dumbest shit humanely possible.
John: Bro I drove 2 hours last night to fuck this fat bitch. Her pussy might've smelt but pussy is pussy.
Eric: Bro, you down bad.
Keaton: "Why won't any of these girls fuck me?"
Collin: "I'm down bad"
Keaton: "I'm so down bad right now"
Damien: " I'm mechanically down bad"
Mathew: "I'm so gay right now"