[1] : The Collaborative International Dictionary of English v.0.48

bough \bough\, n. oe. bogh, as. b=og, b=oh, bough,
   shoulder; akin to icel. b=ogr shoulder, bow of a ship, sw.
   bog, dan. bov, ohg. buog, g. bug, and to gr.?  for ? 
   forearm, skr. b=ahu for bh=aghu arm. root88, 251. cf.
   bow of a ship.
   1913 webster
   1. an arm or branch of a tree, esp. a large arm or main
      branch.
      1913 webster

   2. a gallows. archaic --spenser.
      1913 webster
see also:
bow 

[2] : WordNet (r) 2.0

bough
     n : any of the larger branches of a tree

[3] : Moby Thesaurus II by Grady Ward, 1.0

44 moby thesaurus words for "bough":
   appendage, arm, bine, branch, branchedness, branchiness, burgeon,
   deadwood, flagellum, fork, frond, hand, imp, joint, leg, limb,
   link, lobe, lobule, member, offshoot, organ, pinion, ramage,
   ramification, runner, sarment, scion, shoot, slip, spear, spray,
   sprig, sprit, sprout, spur, stolon, sucker, switch, tail, tendril,
   thallus, twig, wing

Bough >> B Words
Bough, definition of term: Bough
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