Half Homo
It is not "No Homo" nor is it "Completely Homo." It is when a sexual act occurs between two people of the same gender that will not leave the relationship between the two people feeling awkward or strained because of the act, but is too gay to ever be mentioned to anyone besides themselves.
Mark: "Dude, Steve. I think we made out last night."

Steve: "No Homo!"

Mark: "Too late for that dude. Let's just not tell our friends. Half Homo! Whew, if I hadn't called that we'd be really gay right now bro."