Vacillátio, vacillatiônis, f. g. pe. pr. Quint. A wagging or wauering: lewsenesse: inconstancie: inconstant mouing.
Lewis and Short: Latin dictionary
văcillātĭo, ōnis, f. [vacillo], a rocking to and fro, see-saw, a wavering, reeling motion: indecora in dextrum ac laevum latus, Quint. 11, 3, 128: foeda, Suet. Claud. 21 fin.