Lewis & Short

ĭn-accessus, a, um, adj., unapproached, unapproachable, inaccessible (cf.: invius, impervius, devius, avius).

  1. I. Lit. (poet. and post-Aug.): mare scopulis inaccessum, Plin. 12, 14, 30, § 52: montes, id. 6, 28, 32, § 144; 10, 12, 16, § 34; Flor. 3, 1, 14: aditus, Sil. 3, 516: lucus, Verg. A. 7, 11: spelunca radiis solis, id. ib. 8, 195.
  2. II. Trop., unattainable: Pindarus imitationi, Macr. S. 5, 17, 7: formositas, App. M. 4, p. 155.