wimp out 

To back out of something in an especially weak and wimpish manner.

Guy1: "Hey, yo' still coming to the pub tonight? We'll do a gallon and then have a curry!"
Guy2: "I can't now, I've got some letters to write and then I have to wash my hair."
Guy1: "That is a total wimp out bro."

wimp out by Pedrosa von Beagle April 25, 2006

don't wimp out

phrase used in a game much like "punchbuggy" or "monkeys always look". Origin: l'oreal hair products advertisment.

you:"Hey jane?"
Jane:"Yeah?" (or) "what?"
you (pointing your finger at her much like the model on the l'oreal ad):"Don't wimp out!"

you win the stupid game!

don't wimp out by Balki August 14, 2003