The other definitions are correct, in that this means the man gets on all fours and tucks it between his legs so the other person can suck it. Important to note though, this position puts the sucker’s nose DIRECTLY in your ass so it is usually used dismissively.
Friend 1: *sends friend 2 a dick pic*
Friend 2: what the fuck is wrong with you man?
Friend 1: “it’s national send a dick pic to the homies week man.”
Friend 2: “oh, my bad.” *sends a dick pic back*