Top Definition
A very rare animal which is a crossbreed of a bird and hamster. It is a rather large and colorful animal with a unique appearance and sound. Although it looks like a bird, it acts and carries itself like a hamster. It makes a very loud caw sound followed by a series of quiet birmp sounds.

Most sightings are reported in Atlantic City, New Jersey not far from the research facility that was specializing in crossbreeding. People will often do the "AC Caw" in attempt to impersonate this bird.
Guy in an AC Club, "I think that girl is checking me out!"

Friend replies, "You have a better shot with a Birmster!"
Girl walks by and guys do AC Caw... "Ca-Caw!" then turn to each other laugh and make "Birrrmp" noises.
by 302 BFF September 28, 2009

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