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

underdrain \un"derdrain`\, n.
   an underground drain or trench with openings through which
   the water may percolate from the soil or ground above.
   1913 webster

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

underdrain \un`derdrain"\, v. t.
   to drain by forming an underdrain or underdrains in; as, to
   underdrain land.
   1913 webster

Underdrain >> U Words
Underdrain, definition of term: Underdrain
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