Similar to ridonkulous, a combination of preposterous and ridiculous. Possibly originated in the webcomic Wondermark.
Ex. 1:

Man 1: Oh, yeah, we don't say ridonkulous anymore. It isn't cool.
Man 2: THAT'S PREPONDICULOUS.
Man 1: ...

Ex. 2:

Dude, did you hear about how Stacy is going out with Mark again? It's prepondiculous.
by Dee-Lawn November 30, 2007
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