look up any word, like the eiffel tower:
 
1.
Using your thumb to help pleasure a woman cause you can't get it up.
Mart had to much to drink and couldn’t get aroused. So he didn’t disappoint the lady he used his thumb to help get it up there (thumbing it in).

"Like trying to push a Marshmallow into a piggy bank."

"You’ve got it!"
by scratch_nasty October 12, 2011