Peak1  —n. 1 projecting usu. Pointed part, esp.: a the pointed top of a mountain. B a mountain with a peak. C a stiff brim at the front of a cap. 2 a highest point of a curve, graph, etc. (peak of the wave). B time of greatest success, fitness, etc. 3 attrib. Maximum, busiest (peak viewing; peak hours). —v. Reach its highest value, quality, etc. (output peaked).  peaked adj. [related to *pick2]