dossuarius

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.

dossŭārĭus, a, um, adj. [dorsum],

that carries on its back , that bears burdens (very rare): aselli, Varr. R. R. 2, 6 fin. : jumenta, beasts of burden , id. ib. 2, 10, 5.