A large, often excessive amount of pennies, so that there are so many pennies that you attempt to make up for the large amounts of pocket change by contracting the words "plenty" and "pennies."
Friend 1: Hey all I have is a dollar and with tax this costs $1.08. Does anybody have any change?
Friend 2: Of course, I have plennies, would you like some?
Friend 2: Of course, I have plennies, would you like some?
by metallicanroses January 6, 2008
Get the plenniesmug. 
Get the plennymug.