The Collaborative International Dictionary of English v.0.48:

Cayuse \Cay*use"\, n.
   An Indian pony. [Northw. U. S.]
   [1913 Webster] Cazique

WordNet (r) 3.0 (2006):

cayuse
    n 1: a small native range horse [syn: cayuse, Indian pony]

U.S. Gazetteer Places (2000):

Cayuse, OR -- U.S. Census Designated Place in Oregon
   Population (2000):    59
   Housing Units (2000): 22
   Land area (2000):     2.879214 sq. miles (7.457130 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    2.879214 sq. miles (7.457130 sq. km)
   FIPS code:            11900
   Located within:       Oregon (OR), FIPS 41
   Location:             45.675535 N, 118.574012 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Cayuse, OR
    Cayuse