The Collaborative International Dictionary of English v.0.48:

boscage \bos"cage\, n. [OF. boscage grove, F. bocage, fr. LL.
   boscus, buscus, thicket, wood. See 1st Bush.]
   1. A growth of trees or shrubs; underwood; a thicket; thick
      foliage; a wooded landscape.
      [1913 Webster]

   2. (O. Eng. Law) Food or sustenance for cattle, obtained from
      bushes and trees; also, a tax on wood.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "boscage":
   bosket, brake, canebrake, ceja, chamisal, chaparral, coppice,
   copse, copsewood, covert, frith, motte, thicket, thickset,
   underbrush, undergrowth, undershrubs, underwood



Bouvier's Law Dictionary, Revised 6th Ed (1856):

BOSCAGE, Eng. law. That food which wood and trees yield to cattle.