A phrase used without care to insult someone who is homosexual or bisexual. It consists of damn and homo (obviously).
If you hear this phrase, it is most likely to be used by people of the right-wing, conservative political grouping. Generally, they are homophobic and/or Christian. Christian's bible (a fictional tale to keep your life occupied) tell them that gays are looked down upon by Jesus, although he supposedly was also a saint and loved everyone.
To use this phrase is to dislike someone of a lesbian, gay or bisexual sexuality. See homophobic.
Sarah Palin: Hello Joe! I can see Russia from my house!
Liz: Hey, it's Sarah Palin! I support Obama! *is wearing gay pride shirt*
Sarah Palin: Damn homo! Hey, Joe, let's go shoot wolves from my ol' heli!