The Collaborative International Dictionary of English v.0.48:
hayrig \hay"rig\ n. a frame attached to a wagon to increase the amount of hay it can carry. Syn: hayrack, hay rigging. [WordNet 1.5]WordNet (r) 3.0 (2006):
hayrig n 1: a frame attached to a wagon to increase the amount of hay it can carry [syn: hayrack, hayrig]