GashEye is the well tuned art of quickly distinguishing quality vagina from that of lesser quality. Similar to a 'spot the difference' puzzle, it can take several years of intense training in precise longeye gash identification (plgi) to become a master in these arts.
Drew: "your girlfriend's a slut"
Bob: "dude. that's not cool"
Brendan: "dude. hear him out. he's got the gasheye. he knows."