An Assclam is the walk a person does when they have to go to the bathroom. Holding their asscheeks tightly together, like a clam. Sometimes snapping them together quickly to avoid smudge marks. An insult to a person whom walks, or acts funny.
Hey look Chrissy! That guy is an ass clam,I hope he shits himself real good.
Look at his ass clam, he must have to pinch one off, you know sally?