From WordNet (r) 3.0 (2006) [wn]:
waterfall
n 1: a steep descent of the water of a river [syn: waterfall,
falls]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Waterfall \Wa"ter*fall`\, n.
1. A fall, or perpendicular descent, of the water of a river
or stream, or a descent nearly perpendicular; a cascade; a
cataract.
[1913 Webster]
2. (Hairdressing) An arrangement of a woman's back hair over
a cushion or frame in some resemblance to a waterfall.
[1913 Webster]
3. A certain kind of neck scarf. --T. Hughes.
[1913 Webster] Water feather