Wordnet 3.0
ADJECTIVE (1)
1. 
 tamed or trained to obey; 
- Example: "a horse broken to the saddle"- Example: "this old nag is well broken in"[syn: broken, broken in]
WordNet (r) 3.0 (2006):
broken in
    adj 1: tamed or trained to obey; "a horse broken to the saddle";
           "this old nag is well broken in" [syn: broken, broken
           in]