The Collaborative International Dictionary of English v.0.48:
millrace \millrace\ n. a channel from a millpond to a millwheel, to provide the water current that turns the millwheel. Syn: millrun. [WordNet 1.5] Millree MillreaWordNet (r) 3.0 (2006):
millrace n 1: a channel for the water current that turns a millwheel [syn: millrace, millrun]