n A point; the sharp end or top of anything that terminates in a point; as, the peak, or front, of a cap.
n The highest value reached by some quantity in a time period.
n (geography) The top, or one of the tops, of a hill, mountain, or range, ending in a point; often, the whole hill or mountain, especially when isolated; as, the Peak of Teneriffe.
n (nautical) The upper aftermost corner of a fore-and-aft sail; -- used in many combinations; as, peak-halyards, peak-brails, etc.
n (nautical) The narrow part of a vessel's bow, or the hold within it.
n (nautical) The extremity of an anchor fluke; the bill.
n (mathematics) A local maximum of a function, e.g. for sine waves, each point at which the value of y is at its maximum.