D defs.my
Entry 1 sense Webster, 1913

Singletree

· Sin·gle·tree · IPA /ˈsɪŋɡəlˌtɹiː/
01 n. The pivoted or swinging bar to which the traces of a harnessed horse are fixed; a whiffletree.
  1. 1.
    The pivoted or swinging bar to which the traces of a harnessed horse are fixed; a whiffletree.