Definition of doubletree in English:
doubletree
Pronunciation /ˈdəbəlˌtrē/ /ˈdəbəlˌtri/
noun
North American A crossbar in front of a wagon with a swingletree at each end, enabling two horses to be harnessed.
‘The doubletree on the wagon could be adjusted to allow one horse to pull more.’
- ‘The wheel horses pull on the doubletree against this hammerpin running through the wagon-tonque.’
Origin
Mid 19th century from double, on the pattern of singletree.