Knowledge regarding obscure (and usually horribe) bands and movies that makes someone "indy".
Familiarity with independant movements that nobody else knows about or cares about also qualifies as "indy cred".
indie guy #1: since the arctic monkeys are no longer 'indie', i spent all night on google trying to find new indie bands that will be my new favourite band until they become mainstream even though i don't care for the music at all.
indie guy #2: whoa dude, you've got a lot of indy cred. i'm quite indie myself because i only like pre-label bands and i don't listen to anything mainstream.
indie guy #1: i know, we're so indy we even contract the word "independent" and "credibility"!