A unilateral covenant is a one-sided covenant. When God said “I promise, I will never send a flood to destroy the earth again” that was a unilateral covenant. It’s not incumbent on man's behavior. God just said of himself “I promise you I will never do that again”, and that's what made him so mad when they built the Tower of Babel. A unilateral covenant is a one-sided promise, it’s not based on mutual participation, it's not based on mutual agreement; it is one-sided — unilateral.