cave-in noun 3cave in verb 3forms 4 noun3 •The act of something collapsing or caving in.We were warned away from the rickety old mine because of the danger of cave-ins. •The location where something has caved in.We couldn't get past the cave-in blocking the tunnel. •The act of relenting.It was a cave-in, but I let my child have a candy to shut her up. cave in verb3 •To collapse inward or downward.The roof caved in under the weight of the snow. •To cause to collapse inward or downward.He caved in the side of the barrel with a single well-placed kick. •(figurative) To relent; to grant approval against one's initial will.After he asked me a few times, I finally caved in and had a slice of cake. formscaved in · caving in · caves in · cave-ins