A term that often means "crazy", "sick", or "awesome", usually in the context of a party or event. It's commonly used by party kids and tools with "fun-dads" and mainly used in relation to a future tense.
Example 1:

Zac - Ayy dawg you hittin' up dat party tonight in Panama City?
Danny - Hell yeah man iz gon' get so plumsy!

Example 2:

Fun-Dad - Ay boys, ya'll gonna meet some girls tonight on da beach?
Son - Shut up Dad...
Fun-Dad - Haha aightt you boys have fun. Don't get too plumsy though! Ah I just playin' ya'll do whateva, I just want to be your friend and live through you so you can peak in high school.
by AyyyDogfish April 10, 2011
Get the plumsy mug.
An insult. Also referred to as a girls private part
by Abrys October 21, 2007
Get the Plumsy mug.