Lewis & Short

promptŭārĭus (promt-), a, um, adj. [promo],

  1. I. of or belonging to distribution (sc. of things stored up), distributing: arca vestiaria, armarium promptuarium, i. e. storehouse, repository, Cato, R. R. 11, 3: cella, App. Mag. p. 309, 20; and, in comic lang., of a prison, Plaut. Am. 1, 1, 4.
  2. II. Subst.: promptŭārĭum, ĭi, n., a storeroom, repository, promptuary (late Lat.; cf. horreum): e promptuario oleum profer, App. M. 1, p. 113, 2; Ambros. Cantic. 1, 20.
    In plur., Vulg. Psa. 143, 13.
    1. B. Transf.: ornatissimum linguae tuae, i. e. the mouth, Symm. Ep. 9, 67: promptuarium rectae rationis et orationis, App. Dogm. Plat. 1, p. 212 Oud.: cum omnes quasi vetustatis promptuarium Albini memoriam laudavissent, Macr. S. 1, 4, 1.
      Collat. form (from metrical necessity), promptārĭum, ii, Aus. Ep. 21 fin.