finger(s) (rarely toes) that resemble a big, juicy, shaven penis

Sticking a finger in the male urethra for sexual gratification.

A cock so small that it's size is comparable to the size of a finger. (so if you have one, you're better off fingering her, atleast you can double up.)

Or it can be used as an insult.

One who has a fucking damn shitty small~~~~~~~ dick