The Collaborative International Dictionary of English v.0.48:

Kapok \Ka*pok"\, n. [Prob. fr. the native name.] (Bot.)
   A silky wool derived from the seeds of Ceiba pentandra
   (syn. Eriodendron anfractuosum), a bombaceous tree of the
   East and West Indies.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

kapok
    n 1: a plant fiber from the kapok tree; used for stuffing and
         insulation [syn: kapok, silk cotton, vegetable silk]
    2: massive tropical tree with deep ridges on its massive trunk
       and bearing large pods of seeds covered with silky floss;
       source of the silky kapok fiber [syn: kapok, ceiba tree,
       silk-cotton tree, white silk-cotton tree, Bombay ceiba,
       God tree, Ceiba pentandra]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "kapok":
   blubber, breeze, butter, clay, cushion, dough, down, eiderdown,
   feather bed, feathers, fleece, floss, flue, fluff, foam, pillow,
   plush, pudding, puff, putty, rubber, satin, silk, swansdown,
   thistledown, velvet, wax, wool, zephyr