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1.
1. N. A penis which is the approximate size of a peanut. Not a mispelling.
That guy took too many steroids, now he has a peanus.
by Mule_Hammer August 17, 2005
 
2.
A corruption of the word "Peanuts". Originating from a poll on the IGN Boards by user DcPunk, which was meant to be called "What's your favorite type of peanuts".

Instead, the poll looked was asking people to choose between salted or roasted "peanus".

The word has been absorbed as part of standard issue Internet-speak, and literally means "penis".
OMG uRghey now stik ur peanus in my but kthx
by Mr_eX September 08, 2003