What exactly is a “cheese” in Starcraft 2?
What is the definition of a "cheese build", specifically with reference to standard SC2 builds? Where did the term "cheese build" originate?
A cheese build is any build that is generally unstable in the long-run, but is used to exploit a single weakness.
The term "cheese build" is closely related to the term "cheesy".
Here's a good guide on the term