[UNDER-1 5 c.] An underground drain.
1805. R. W. Dickson, Pract. Agric., I. 151. Where underdrains are formed for taking off the water below the footways.
1868. Rep. U.S. Commissioner Agric. (1869), 354. The longitudinal underdrains are to be made of broken stones, and are to be filled up to the level of the surface.
