peak¹ (pēk)
n.

1. A tapering, projecting point; a pointed extremity: the peak of a cap; the peak of a roof.
2. (Abbr. Pk.)
   1. The pointed summit of a mountain.
   2. The mountain itself.
3. 1. The point of a beard.
   2. 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.
   1. The narrow portion of a ship's hull at the bow or stern.
   2. The upper after corner of a fore-and-aft sail.
   3. 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.]

peak² (pēk)
intr.v., peaked, peak·ing, peaks.
To become sickly, emaciated, or pale.

[Origin unknown.]

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The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.

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