The Collaborative International Dictionary of English v.0.48:

Boll \Boll\, n. [OE. bolle boll, bowl, AS. bolla. See Bowl a
   vessel.]
   1. The pod or capsule of a plant, as of flax or cotton; a
      pericarp of a globular form.
      [1913 Webster]

   2. A Scotch measure, formerly in use: for wheat and beans it
      contained four Winchester bushels; for oats, barley, and
      potatoes, six bushels. A boll of meal is 140 lbs.
      avoirdupois. Also, a measure for salt of two bushels.
      [Sometimes spelled bole.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Boll \Boll\, v. i. [imp. & p. p. Bolled.]
   To form a boll or seed vessel; to go to seed.
   [1913 Webster]

         The barley was in the ear, and the flax was bolled.
                                                  --Ex. ix. 31.
   [1913 Webster]

WordNet (r) 3.0 (2006):

boll
    n 1: the rounded seed-bearing capsule of a cotton or flax plant

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "boll":
   ball, balloon, bladder, blob, bolus, bubble, bulb, bulbil, bulblet,
   burr, capsule, cod, ellipsoid, follicle, geoid, globe, globelet,
   globoid, globule, glomerulus, gob, gobbet, hull, husk, knob, knot,
   legume, legumen, oblate spheroid, orb, orbit, orblet, pease cod,
   pellet, pericarp, pod, prolate spheroid, rondure, seed pod,
   seed vessel, seedbox, seedcase, silique, sphere, spheroid,
   spherule