Beer guzzling, fag
smoking, curry eating woman.
A geezer bird enjoys a good honest night down the pub, and is able to hold her own in a laddish conversation. Men tell her they like her because she is "up for it" - this is the highest compliment a man can give.
Of course, a proper geezer bird is simultaneously laddish and attractive.
Being told you are a geezer bird by a man is like being told:
"While I find you to be an attractive woman, I enjoy the fact that you are not too uptight to laugh when I ask whether you have had more pricks in you than a second-hand dartboard."