Lewis & Short

pĕnē̆trālis, e, adj. [penetro].

  1. I. Piercing, penetrating (ante-class.): frigus, Lucr. 1, 494: ignis, id. 1, 535: fulmineus multo penetralior ignis, id. 2, 382.
  2. II. Transf., inward, inner, internal, interior, innermost (mostly poet.): tecta, Verg. G. 1, 379: aeternumque adytis effert penetralibus ignem, id. A. 2, 297: abditi ac penetrales foci, Cic. Har. Resp. 27, 57: di Penates … ab eo, quod penitus insideret: ex quo etiam penetrales a poëtis vocantur, id. N. D. 2, 27, 68; so, per penetrales deos, Sen. Oedip. 265; id. Phoen. 340: penetrale sacrificium dicitur, quod interiore parte sacrarii conficitur: unde et penetralia cujusque dicuntur; et penes nos, quod in potestate nostrā est, Fest. p. 250 Müll.
    As subst.: pĕnē̆trāle, is (pĕnē̆tral, Macr. S. 7, 1; Symm. Ep. 2, 34), n.; usually in plur.: pĕnē̆trālĭa, ium, the inner part, interior of any thing, esp. of a building; the inside space, an inner room (mostly poet.; not in Cic. or Cæs.; cf. adytum).
  1. I. Lit.
    1. A. In gen.: penetrale urbis, Liv. 41, 20, 7: in ipsis penetralibus (Britanniae), Tac. Agr. 30: apparent Priami et veterum penetralia regum, the inner chambers, Verg. A. 2, 484: in penetralibus regum ipsorum, Vulg. Psa. 104, 30; so, penetralia alta medio tecti, Verg. A. 7, 59: magni amnis penetralia, Ov. M. 1, 574; Sil. 7, 501.
    2. B. In partic.
      1. 1. A sanctuary, esp. that of the Penates, a chapel: penetralia sunt penatium deorum sacraria, Fest. p. 208 Müll.: Capitolini Tonantis, Mart. 10, 51.
      2. 2. Transf., poet., the Penates, guardian deities: huc vittas castumque refer penetrale parentum, Sil. 13, 62: avi penetralia Turni, id. 1, 668.
  2. II. Trop., an inner place, secret place, a secret (post-Aug.), Stat. S. 3, 5, 56: loci aperire penetralia, Quint. 6, 2, 25: auxilia ex ipsis sapientiae penetralibus petere, id. 12 prooem. § 3: animus secedit in loca pura … Haec eloquentiae penetralia, Tac. Or. 12: penetralia animi, Ambros. in Luc. 1, 1, 12: mentis, id. ib. 1, 5, 105.
    With esp. reference to the signif. sanctuary (v. supra, I. B.): ut tantum intra suum penetral existimes adorandam (philosophiam), Macr. S. 7, 1: sanctum penetral animi tui nesciunt, Symm. Ep. 2, 34.
    Adv.: pĕnē̆trālĭter, inwardly, internally (post-class.), Ven. Vit. S. Mart. 4, 597.