an informer; rat.
a person who betrays, denies, or abandons his or her associates, social group, beliefs, etc.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for cheese eater
Historical Examples of cheese eater
A Greek author has described the Crow as a cheese-eater—but that's a fable.