(mathematics, engineering) A function or waveform that repeatedly ramps upwards (usually linearly) and then sharply drops.

(mathematics, engineering) A function or waveform that alternately ramps linearly upwards and then downwards.

Highly vocal and visible support given to a cause. / (television) Undesirable horizontal skewing of frames in a video signal.

An electromagnetic wave of constant amplitude and frequency, typically a sine wave, that for mathematical analysis is considered to be of infinite duration.

A subdued waving gesture used by the British royal family to acknowledge the public.

A natural phenomenon in the atmospheres and oceans of planets, a kind of inertial wave that is largely due to planetary rotation.

(surfing) To mount one's surfboard at a distance from shore, turn it toward land, and control it for a successful, satisfying ride on inrushing water.

A method of curling the hair by pinching it between the fingers and combing in alternate directions.

(virology) A phenomenon that can develop during a pandemic where after a group recovers and infections appear to decrease, another group becomes infected and causes a recurrence in cases.

(historical, physics) a quantum of light, a photon, an electromagnetic wave -- understood as being a disturbance in the æther, a substance believed to provide the medium for light in vacuum