VAC'ILLATE, verb intransitive [Latin vacillo; Eng. to waggle, a diminutive of wag. See Wag.] 1. To waver; to move one way and the other; to reel or stagger. 2. To fluctuate in mind or opinion; to waver; to be unsteady or inconstant.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI