Gash Mole is a derogatory word use to define sluts (for the female) or dickheads (for the male).
For the female, it is when you see a girl that is so obviously a slut that you want to yell out 'show us your Gash you Mole" but instead you just use the less offensive, shortened warcry "Gashmole!"
For the male, it is when your friend is being such a pussy in certain situations that their head transforms into a giant vagina, you are forced to say "Gashmole!".
youve become the worst kind of Gash Mole