UNDULA'TION, noun [from undulate.] 1. A waving motion or vibration; as the undulations of a fluid, of water or air; the undulations of sound. The undulations of a fluid are propagated in concentric circles. 2. In medicine, a particular uneasy sensation of an undulatory motion in the heart. 3. In music, a rattling or jarring of sounds, as when discordant notes are sounded together. It is called also beat. 4. In surgery, a certain motion of the matter of an abscess when pressed, which indicates its maturity or fitness for opening.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI