Lewis & Short

Vandălĭi or Vandĭli or Vandĭlĭi, ōrum, m., the Vandals, a people in the northern part of Germany in the time of Tacitus, Tac. G. 2 (Vandalii, Halm; Vandilii, Ritter); Plin. 4, 14, 28, § 99 (Vandili, Jan. and Sillig).
Sing.: Vandalus, a Vandal, Sid. Carm. 2, 369.
Hence,

  1. A. Vandălus, a, um, adj., Vandal: hostis, Sid. Carm. 2, 348.
  2. B. Vandălĭcus, i, m., a surname of Justinian, as conqueror of the Vandals, Jornand. R. Get. fin.