Also can be used to describe someone who has a particularly large set of genitals OR a feeling of overall positive excitement over an issue.
Vern: "Hey Terry, did you see that girl in the orange shirt?"
Terry: "Oh man, definitely. I saw her and immediately got bigNDpants."
"After Brett saw Jared's dick he immediately bestowed Jared with the nickname 'bigNDpants.'
Brock: "Have you played the demo for Resident Evil 5 yet?"
Payton: "All the time! Now I'm definitely bigNDpants for the full game to arrive!"