peak 1 
(pēk)
(pēk)n.
1. A tapering, projecting point; a pointed extremity: the peak of a cap; the peak of a roof.
2.
a. The pointed summit of a mountain.
b. The mountain itself.
3.
a. The point of a beard.
b. A widow's peak.
4. The point of greatest development, value, or intensity: a novel written at the peak of the writer's career. See Synonyms at summit.
5. Physics The highest value attained by a varying quantity: a peak in current.
6. Nautical
a. The narrow portion of a ship's hull at the bow or stern.
b. The upper aft corner of a quadrilateral fore-and-aft sail.
c. The outermost end of a gaff.
v. peaked, peak·ing, peaks
v.tr.
1. Nautical To raise (a gaff) above the horizontal.
2. To bring to a maximum of development, value, or intensity.
v.intr.
1. To be formed into a peak or peaks: Beat the egg whites until they peak.
2. To achieve a maximum of development, value, or intensity: Sales tend to peak just before the holidays.
adj.
Approaching or constituting the maximum: working at peak efficiency.
[Probably Middle English pike, peke; see PIKE5.]