The Collaborative International Dictionary of English v.0.48:

Canon \Ca*[~n]on"\ (k[aum]*ny[-o]n"; anglicized k[a^]n"y[u^]n),
   n. [Sp., a tube or hollow, fr. ca[~n]a reed, fr. L. canna.
   See Cane.]
   A deep gorge, ravine, or gulch, between high and steep banks,
   worn by water courses. [Mexico & Western U. S.] [Also spelled
   canyon.]
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Canyon \Can"yon\, n.
   The English form of the Spanish word Ca[~n]on.
   [1913 Webster]

WordNet (r) 3.0 (2006):

canyon
    n 1: a ravine formed by a river in an area with little rainfall
         [syn: canyon, canon]