1. (not in technical use) a large, destructive ocean wave, produced by a seaquake, hurricane, or strong wind. Cf. tsunami. 2. either of the two great wavelike swellings of the ocean surface that move around the earth on opposite sides and give rise to tide, caused by the attraction of the moon and sun.
3. any widespread or powerful movement, opinion, or tendency: a tidal wave of public indignation.