When 2 men are in a spooning position, one of the men spreads their ass and the other guy smacks his dick on the other guys ass while yelling caterpillar.
Guy 1: Hey, lay on your side and spread your cheeks
A woman that has tons of back fat and wears tight shirts which gives the appearance of a caterpillar in motion. Her very presence makes the penis soft.
That newbroad in HR has a caterpillar back. She makes me gag with rage and hatred, how I loathe her fat back.