A vagina that is much bigger on the inside than it appears to be on the outside like the tardis of dr. Who. Normally found on athletic girls who appear "tight" upon cursory inspection, the Tardis Pussy can kill your boner faster than a dalek hell bent on extermination.
"I met the hottest girl at spin class, her body was perfect. After a few drinks we went back to my place and had sex."
-"was she nice and tight from all the spinning?"
"nope. She had a tardis pussy. It was tiny and cute but It was like siding my penis directly into the miky way galaxy."