Definition of "packhorse"

Finally they put him on one of De Soto's packhorses, but even on a packhorse his feet hung down to within a few inches of the ground.

1997, Knights of Spain, Warriors of the Sun: Hernando de Soto and the South's Ancient Chiefdoms, page 232

Procter had a handsome half-breed girl with him and two splendid elk heads and meat on his packhorses that he was taking to Fort Lincoln for sale.

2009, Victor Grant Smith, edited by Jeanette Prodgers, The Champion Buffalo Hunter: The Frontier Memoirs of Yellowstone Vic Smith, Revised edition, page 70

While I was destroying my parka, the packhorse that Bob had been leading laid down. So now all our supplies were supine along with the napping packhorse. Looking upon a reclining packhorse while facing a wind-driven rain, wearing a tattered rain parka, with lightning flashing every fifteen seconds followed by thunder so loud my clothes shuddered was not how I had expected the afternoon to unfold. Each time we got the packhorse to his feet he would promptly lie down again.

2010, Bill G. Yung, The Half Fast Hunter, page 41