when a girl takes it from behind from one guy and gives a blowjob to another guy. thus forming a human h.
Ray: so what'd you end up doing friday
Joe: we human h'ed that bitch
When two dudes tape their erect penises together. Thus forming an "H".
"Hey, Gary, do you wanna come over to my house tonight and do the Human H for me and put it on GayTube.net? You bring the scotch tape."