noun
The definition of a guideline is something used to define how a judgment or policy is made.
An example of a guideline is all actors trying out for a part by performing a scene made popular by a famous actor.
guideline

a standard or principle by which to make a judgment or determine a policy or course of action
guideline

noun
A statement or other indication of policy or procedure by which to determine a course of action: guidelines for the completion of tax returns.
guideline

Noun
(plural guidelines)