the iron or strap on the shaft of a horse-drawn vehicle to which the breeching of the harness is attached, enabling the horse to hold back or to back the vehicle.

a device for restraining or checking, as a doorstop or tieback.

a stop or delay

a holdback in negotiations.

a withholding

the holdback of a day's pay.

something, as a planned expenditure or allotment, that is withheld or deferred.