Lewis & Short

undātim, adv. [undo],

  1. I. in a waving manner, like waves: mensae undatim crispae, Plin. 13, 15, 30, § 96: crispum marmor, id. 36, 7, 11, § 55.
  2. II. In a throng, Amm. 21, 3, 2.