The Collaborative International Dictionary of English v.0.48:

Flax \Flax\ (fl[a^]ks), n. [AS. fleax; akin to D. vlas, OHG.
   flahs, G. flachs, and prob. to flechten to braid, plait,m
   twist, L. plectere to weave, plicare to fold, Gr. ? to weave,
   plait. See Ply.]
   1. (Bot.) A plant of the genus Linum, esp. the L.
      usitatissimum, which has a single, slender stalk, about a
      foot and a half high, with blue flowers. The fiber of the
      bark is used for making thread and cloth, called linen,
      cambric, lawn, lace, etc. Linseed oil is expressed from
      the seed.
      [1913 Webster]

   2. The skin or fibrous part of the flax plant, when broken
      and cleaned by hatcheling or combing.
      [1913 Webster]

   Earth flax (Min.), amianthus.

   Flax brake, a machine for removing the woody portion of
      flax from the fibrous.

   Flax comb, a hatchel, hackle, or heckle.

   Flax cotton, the fiber of flax, reduced by steeping in
      bicarbonate of soda and acidulated liquids, and prepared
      for bleaching and spinning like cotton. --Knight.

   Flax dresser, one who breaks and swingles flax, or prepares
      it for the spinner.

   Flax mill, a mill or factory where flax is spun or linen
      manufactured.

   Flax puller, a machine for pulling flax plants in the
      field.

   Flax wench.
      (a) A woman who spins flax. [Obs.]
      (b) A prostitute. [Obs.] --Shak.

   Mountain flax (Min.), amianthus.

   New Zealand flax (Bot.) See Flax-plant.
      [1913 Webster]

WordNet (r) 3.0 (2006):

flax
    n 1: fiber of the flax plant that is made into thread and woven
         into linen fabric
    2: plant of the genus Linum that is cultivated for its seeds and
       for the fibers of its stem

Easton's 1897 Bible Dictionary:

Flax
   (Heb. pishtah, i.e., "peeled", in allusion to the fact that the
   stalks of flax when dried were first split or peeled before
   being steeped in water for the purpose of destroying the pulp).
   This plant was cultivated from earliest times. The flax of Egypt
   was destroyed by the plague of hail when it "was bolled", i.e.,
   was forming pods for seed (Ex. 9:31). It was extensively
   cultivated both in Egypt and Palestine. Reference is made in
   Josh. 2:6 to the custom of drying flax-stalks by exposing them
   to the sun on the flat roofs of houses. It was much used in
   forming articles of clothing such as girdles, also cords and
   bands (Lev. 13:48, 52, 59; Deut. 22:11). (See LINEN.)