Lewis & Short

Armĭlustrum, i, n., a place in Rome (in the 13th district), where was celebrated the festival Armilustrium, consecration of arms, ὁπλοκαθαρμός (19th Oct.; v. Inscr. Orell. II. p. 411): Armilustrum ab ambitu lustri, Varr. L. L. 5, § 153 Müll.; Liv. 27, 37: armilustrium ab eo, quod in armilustrio armati sacra faciunt, Varr. L. L. 6, § 22 Müll.; Paul. ex Fest. p. 19 Müll.