Big Bird is a slang term for the grocery store Giant Eagle

a big ass yellow homosexual bird from a little kids show

It is the pimp yellow bird from sesame street.
It can also be mainly be described as any kind of mutlipurpose helicopters. Though they may be big the big birds have no chance of taking on a little bird helicopter.

The big middle finger

The sexual act of eating a dozen eggs (either cooked or raw), then vomiting the rubbery yellow mess onto your partner's chest.

Similar to a Cosby Sweater, in that both cause your partner to resemble beloved childhood icons.

(verb) to explain a maddeningly simple concept to some poor interloper with a mile-thick skull. At times you feel like a Sesame Street character demonstrating the art of bubble blowing to an audience of half a million bile-stained, catatonic 2-year-olds.

a twat that always has her legs open for everyone

a large white female who has a huge nose