A penis - particularly a penis that is curious and/or searching for something. The gorilla thumb might be particularly hairy or thick, although not necessarily. Ideally, it doesn't have a fingernail.
by bullfrogboy January 20, 2009

'Ohh yes winter is here and the girls are out and about. There's Gorilla's thumbs all over the place'
by Mongymax November 13, 2007

by JimboSlice13 July 14, 2017
