n. 车前横木

[ noun ]
a crossbar that is attached to the traces of a draft horse and to the vehicle or implement that the horse is pulling
<noun.artifact>

Whippletree \Whip"ple*tree`\, n. [See {Whip}, and cf.
{Whiffletree}.]
1. The pivoted or swinging bar to which the traces, or tugs,
of a harness are fastened, and by which a carriage, a
plow, or other implement or vehicle, is drawn; a
whiffletree; a swingletree; a singletree. See
{Singletree}.

[People] cut their own whippletree in the woodlot.
--Emerson.

2. (Bot.) The cornel tree. --Chaucer.