cramp

A cramp is a painful contraction of the muscle that cannot be controlled.

Example: Quick, save him! He is having muscle cramps and is about to drown in the water!

If a muscle cramps, it contracts in a painful way.

Example: My legs cramped in the middle of my run.

If you are cramped by something, you are restricted by it in some way; you are not able to move around or express things.