rilln.[Cf. LG. rille a small channel or brook, a furrow, a chamfer, OE. rigol a small brook, F. rigole a trench or furrow for water, W. rhill a row, rhigol a little ditch. 11.]1. A very small brook; a streamlet.()2. (Astron.) See Rille.()v. i. To run a small stream.(Prior.)