The Collaborative International Dictionary of English v.0.48:

Saddlecloth \Sad"dle*cloth`\ (?; 115), n.
   A cloth under a saddle, and extending out behind; a housing.
   [1913 Webster]

WordNet (r) 3.0 (2006):

saddlecloth
    n 1: stable gear consisting of a blanket placed under the saddle
         [syn: saddle blanket, saddlecloth, horse blanket]