Definify.com
Webster 1913 Edition
Underdrain
Un′der-drainˊ
,Noun.
An underground drain or trench with openings through which the water may percolate from the soil or ground above.
Unˊder-drain′
,Verb.
T.
To drain by forming an underdrain or underdrains in;
as, to
. underdrain
landWebster 1828 Edition
Underdrain
UN'DERDRAIN
,Noun.