peak

Concise Oxford English Dictionary © 2008 Oxford University Press:
peak1

▶noun

• 1 the pointed top of a mountain.

  ■ a mountain with a peak.

• 2 the point of highest activity or achievement.

  ■ a point in a curve or on a graph, or a value of a physical quantity, which is higher than those around it.

• 3 Brit. a stiff brim at the front of a cap.

• 4 the upper, outer corner of a sail extended by a gaff.

▶verb reach the highest point. ▶adjective maximum or utmost: at peak fitness.

■ characterized by maximum activity or demand: peak hours.

– derivatives
peakless adjective.

– origin C16: prob. a back-form. from peaked, var. of dial. picked ‘pointed’.

Concise Oxford English Dictionary © 2008 Oxford University Press:
peak2

▶verb archaic decline in health and spirits.

– origin C17: of unknown origin.