The Collaborative International Dictionary of English v.0.48:

Follicle \Fol"li*cle\, n. [L. folliculus a small bag, husk, pod,
   dim of follis bellows, an inflated ball, a leathern money
   bag, perh. akin to E. bellows: cf. F. follicule. Cf. 2d
   Fool.]
   1. (Bot.) A simple podlike pericarp which contains several
      seeds and opens along the inner or ventral suture, as in
      the peony, larkspur and milkweed.
      [1913 Webster]

   2. (Anat.)
      (a) A small cavity, tubular depression, or sac; as, a hair
          follicle.
      (b) A simple gland or glandular cavity; a crypt.
      (c) A small mass of adenoid tissue; as, a lymphatic
          follicle.
          [1913 Webster]

WordNet (r) 3.0 (2006):

follicle
    n 1: any small spherical group of cells containing a cavity

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "follicle":
   alveolation, alveolus, antrum, armpit, basin, boll, bowl, burr,
   capsule, cavity, cod, concave, concavity, crater, crypt, cup,
   depression, dip, fold, funnel chest, hole, hollow, hollow shell,
   hull, husk, lacuna, legume, legumen, pease cod, pericarp, pit,
   pocket, pod, punch bowl, scoop, seed pod, seed vessel, seedbox,
   seedcase, shell, silique, sink, sinus, socket, trough, vug