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. (Science: botany) The cornel tree.