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

baldachin \bal"dachin\, n. ll. baldachinus, baldechinus, a
   canopy of rich silk carried over the host; fr. bagdad, it.
   baldacco, a city in turkish asia from whence these rich silks
   came: cf. it. baldacchino. cf. baudekin.
   1. a rich brocade; baudekin. obs.
      1913 webster

   2. arch. a structure in form of a canopy, sometimes
      supported by columns, and sometimes suspended from the
      roof or projecting from the wall; generally placed over an
      altar; as, the baldachin in st. peter's.
      1913 webster

   3. a portable canopy borne over shrines, etc., in procession.
      1913 webster written also baldachino, baldaquin,
      etc.
      1913 webster
see also:
baudekin baldachino baldaquin 

[2] : WordNet (r) 2.0

baldachin
     n : ornamented canopy supported by columns or suspended from a
         roof or projected from a wall as over an altar

Baldachin >> B Words
Baldachin, definition of term: Baldachin
baldachin_pag1.html