1. A period of time during a dispute wherein the parties involved do not communicate with one another as a means of reducing hostility and/or reconsidering their positions before taking further action. I think we both need a cooling-off period before one of us says something that we don't mean.

2. The time allowed after a purchase or the signing of a contract in which the buyer/signer may return the product or back out of the agreement without penalty or fee. I'm glad I had that cooling-off period after buying that sports car—there's no way I can actually afford it!

3. The period of time for which waste from nuclear fuel must be allowed to cool in water before being safely reprocessed or sent for permanent storage. If waste is not allowed its full cooling-off period, it could contaminate the environment and poison people.