1. An act that is absolutely and unforgivably embarrassing.
2. Can also describe an individual who is a low-life and lame.
Origins: Comes from the origins of peasant, which inevitably over time became pheasant. Only natural that it become birdish.
John: (makes an incredibly bad golf shot)
Earl: That was downright birdish!
Susie: What is a Dutch Master?
Kelly: Silly girl, it's only America's premier smoking apparatus don't be birdish.