Search Result for "doubletree": 
Wordnet 3.0

NOUN (1)

1. a crossbar on a wagon or carriage to which two whiffletrees are attached in order to harness two horses abreast; 



The Collaborative International Dictionary of English v.0.48:

Doubletree \Dou"ble*tree`\, n.
   The bar, or crosspiece, of a carriage, to which the
   singletrees are attached.
   [1913 Webster]


WordNet (r) 3.0 (2006):

doubletree
    n 1: a crossbar on a wagon or carriage to which two whiffletrees
         are attached in order to harness two horses abreast