The Collaborative International Dictionary of English v.0.48:
Rivulet \Riv"u*let\, n. [Earlier rivolet, It. rivoletto, a dim. fr. rivolo, L. rivulus, dim. of rivus a brook. CF. Rival, Rite.] A small stream or brook; a streamlet. [1913 Webster] By fountain or by shady rivulet He sought them. --Milton. [1913 Webster]WordNet (r) 3.0 (2006):
rivulet n 1: a small stream [syn: rivulet, rill, run, runnel, streamlet]