the act of hitting someone in the ass particularly hard using your knee while holding their shoulders with your hands and yelling "elephant boner!" upon impact of the knee into said ass.
Man i shouldn't have turned away from Jacob, he gave me a really hard elephant boner.
The act of placing either of your elbows forward while using your free arm for support, and running full speed into another person's back, preferably above their ass (No one wants ass on their arms). Remember to add insult to injury by shouting, "Elephant boner!" when the deed is done.
Not suspecting a thing, Ted willingly turned his back on Greg, only to be rewarded with a stern elephant boner to the kidney.
Greg: ELEPHANT BONER! HAAA ha ha ha haaa!!!