What does ANCIENT WATER-COURSE mean? October 16, 2017 All Dictionary ANCIENT WATER-COURSE meaning in Law Dictionary water-course is "ancient" in the event that channel through which it normally runs features been around from since the beginning independent of the level of liquid which it discharges. Earl v. De Ilart. 12 N. .T. Eq. 280. 72 Am. Dec. 305.