1. A category of vibrators that are particularly large and threatening. They can be identified by the warning colors that they have evolved over time, usually ones that are not normally found in nature.
2. A threat used to strike fear in the hearts and colons of straight men.
1. The noise from my roommate's Purple Monster kept me awake all night, and she lives on the other side of the house!
2. If you keep pissing me off, I'll use the Purple Monster on you!