Shakespear explained: As well as being the surname of a famous Playwright (William Shakespear), it is used as a double meaning to insult something, calling someone a Shakespeare is calling Someone who "shakes their spear" in other words plays with themself.
A Work of Shakespear - Wank stain (ejectulation)
Also can be a Macbeth, or a Hamlet or even a Romeo & Juliet
Meaning: Stop being such a wanker.
Guy 1: "Do you remember Guy?"
Guy 2: "Guy, isn't he the Shakespear we went to school with?"
Guy 1: "Yeah that's him."
Meaning: Guy, isn't he the wanker we went to school with?