Singletree
Pronunciation : Sin"gle*tree`
Part of Speech : n.
Etymology : [Cf. Swingletree.]
Definition : Defn: The pivoted or swinging bar to which the traces of a harnessed horse are fixed; a whiffletree.
Note: When two horses draw abreast, a singletree is fixed at each end of another crosspiece, called the doubletree.
Source : Webster's Unabridged Dictionary, 1913