Lewis & Short

extensĭo, ōnis, f. [extendo].

  1. I. A stretching out, extension.
    1. A. Lit.: chordarum, Isid. 3, 15, 1.
      Esp. of the body or limbs: corporum, Cael. Aur. Acut. 3, 6, 63; id. Tard. 2, 1, 2; 3; 14; 16: crurum, id. ib. 2, 1, 44; so, alarum, a spreading, Vulg. Isa. 8, 8: membranae (in a water-fowl’s foot), Ambros. Hexaem. 5, 22, 74: follis nostri corporei, Arn. in Psa. 149.
    2. B. Transf.
          1. (α) A swelling, tumor: extensiones et tubercula in dorso, Veg. 3, 15, 2.
          2. (β) An extension, extended space: caelorum, Hier. in Isa. 12, 44, § 24.
  2. II. Trop., a strain, stretching: mentis = ἔκστασις, i. e. fury, Cael. Aur. Tard. 1, 5, 150.