A parody in contemporary usage, is a work created to mock, comment on, or make fun at an original work, its subject, author, style, or some other target, by means of humorous, satiric or ironic imitation. Waiting for Godot is not a parody meant for humor. If Beckett is parodying anything, he is parodying traditional expectations of theatre for the purpose of surprising and 'disturbing' his audience into a new mind frame as it relates to how a playwright accomplishes his task.
A traditional play has several characters, lots of action, a forward motion of action, a setting that is probably visually interesting, a clear climax (moment of no return) and a clear resolution of the conflict(s). This play has only the sketch of these elements. There are only two main characters and only three others who appear and have almost NO effect on the main characters. The setting is the bare minimum of a tree and a rock in an otherwise empty landscape. There is no moment of climax. The play has no resolution; it literally ends where it begins with two men sitting at the side of the road waiting for a man named Godot whom they hope will tell them what to do. He never appears and we assume he never will. The play is incredibly bleak and ultimately absurd. Absurd theatre challenges the notions of time, place, unity, and logic in drama -- it takes the traditions, and parodies them in order to make its point. In this case, the point is an existential study of man in the modern world.