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

sapwood \sap"wood`\, n. bot.
   the alburnum, or part of the wood of any exogenous tree next
   to the bark, being that portion of the tree through which the
   sap flows most freely; -- distinguished from heartwood.
   1913 webster
see also:
heartwood 

[2] : WordNet (r) 2.0

sapwood
     n : newly formed outer wood lying between the cambium and the
         heartwood of a tree or woody plant; usually light
         colored; active in water conduction

Sapwood >> S Words
Sapwood, definition of term: Sapwood
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