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2.
a small latex cap, resembling a condom, that unrolls over the tip of a caulk tube to prevent it from drying up; also known as a Red Cap
Dammit! Pauly forgot to put a monkey rubber on that expensive tube of elastomeric caulk and now it's gone to shit!
by ATown Social Experiment July 10, 2008
 
1.
A perverted sexual act, where the individual masturbates whilst watching animals shagging.

This can be done in a zoo
or whilst at home maybe watching porn off the animal variety.
number 1: "Did you hear about Dave?"

number 2: "Yeah i know turns out he's a monkey rubber."
by sir david attenborough the 2nd December 28, 2007