Holdback

Part of speech: noun (n.)

1. Check; hindrance; restraint; obstacle. The only holdback is the affection . . . that we bear to our wealth. Hammond.

2. The projection or loop on the thill of a vehicle. to which a strap of the harness is attached, to hold back a carriage when going down hill, or in backing; also, the strap or part of the harness so used.