The Collaborative International Dictionary of English v.0.48:

Distend \Dis*tend"\, v. i.
   To become expanded or inflated; to swell. "His heart distends
   with pride." --Milton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Distend \Dis*tend"\, v. t. [imp. & p. p. Distended; p. pr. &
   vb. n. Distending.] [L. distendere, distentum, distensum;
   dis- + tendere to stretch, stretch out: cf. F. distendre to
   distend, d['e]tendre to unbend. See Tend, and cf.
   Detent.]
   1. To extend in some one direction; to lengthen out; to
      stretch. [R.]
      [1913 Webster]

            But say, what mean those colored streaks in heaven
            Distended as the brow of God appeased? --Milton.
      [1913 Webster]

   2. To stretch out or extend in all directions; to dilate; to
      enlarge, as by elasticity of parts; to inflate so as to
      produce tension; to cause to swell; as, to distend a
      bladder, the stomach, etc.
      [1913 Webster]

            The warmth distends the chinks.       --Dryden.

   Syn: To dilate; expand; enlarge; swell; inflate.
        [1913 Webster]

WordNet (r) 3.0 (2006):

distend
    v 1: become wider; "His pupils were dilated" [syn: dilate,
         distend]
    2: cause to expand as it by internal pressure; "The gas
       distended the animal's body"
    3: swell from or as if from internal pressure; "The distended
       bellies of the starving cows"

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "distend":
   add to, aggrandize, amplify, augment, bag, balloon, belly,
   belly out, bilge, billow, bloat, blow up, bouge, broaden, bug,
   build, build up, bulge, bulk, bulk out, crescendo, develop, dilate,
   enlarge, expand, extend, fill out, goggle, greaten, hike, hike up,
   huff, increase, inflate, lengthen, magnify, pooch, pop, pouch,
   pout, puff, puff up, pump, pump up, raise, rarefy, round out,
   snowball, stretch, sufflate, swell, swell out, tumefy, up, widen