1. An expression used to indicate disgust with homophobic individuals' assumptions that if someone is gay they will do everything differently from a heterosexual person. Often this disgust is lost on the offending homophobe.
2. Less frequently used as a euphemism for someone who is flamboyantly gay.
Also sometimes used as "gay/ing up the lawn".
This guy called me at the lawn service business where I work. He said he had heard I was gay and wanted to prove he "ain't no homophobe". He actually asked me if I could come "gay up 'his' lawn, or whatever it is 'I' do".
Some bitch at the supermarket saw me and John holding hands. She asked us if we cuddled each other after sex. I told her I'd schedule a time to answer her question, right after I finished gaying up my lawn.
Sue: Rob, you're a homo... you'd be great at helping me pick out a dress for my date tonight!
Rob: "Love" to, Sue... But I can't. I'm committed to gaying up my lawn tonight...
Jessica: So how did it go when you came out to your mother.
Jill: It really wasn't too bad. She doesn't seem to be worried I'll be gaying up my lawn or anything.
Josh would be a lot more fun to hang out with if he wasn't constantly gaying up his lawn...