Thill \Thill\, n. [OE. thille, AS. ?ille a board, plank, beam, thill; akin to ?el a plank, D. deel a plank, floor, G. diele, OHG. dili, dilla, Icel. ?ilja a plank, planking, a thwart, ?ili a wainscot, plank; cf. Skr. tala a level surface. [root]236. Cf. Fill a thill, Deal a plank.]

1. One of the two long pieces of wood, extending before a vehicle, between which a horse is hitched; a shaft.

2. (Mining) The floor of a coal mine. --Raymond.

Thill coupling, a device for connecting the thill of a vehicle to the axle.

Source: Webster's Revised Unabridged Dictionary (1913)