1. (Anat.) (a) A sheath; a theca; as, the vagina of the portal vein.
(b) Specifically, the canal which leads from the uterus to the external
orifice if the genital canal, or to the cloaca.
2. (Zoöl.) The terminal part of the oviduct in insects and various
other invertebrates. See Illust., of Spermatheca.
3. (Bot.) The basal expansion of certain leaves, which inwraps the
stem; a sheath.
4. (Arch.) The shaft of a terminus, from which the bust of figure seems
to issue or arise.