Wordnet 3.0
NOUN (1)
1. 
 a channel in which a tidal current runs; 
The Collaborative International Dictionary of English v.0.48:
Tideway \Tide"way`\, n.
   Channel in which the tide sets.
   [1913 Webster]
WordNet (r) 3.0 (2006):
tideway
    n 1: a channel in which a tidal current runs