one straw bagful; one bale
A counter for traditional straw bags (俵) used for rice, charcoal, etc. Often used in historical or agricultural contexts.
I bought one bale of rice from the farmer.
俵 is the straw bag itself; 一俵 is the counter for one such bag.
Compound of 一 (いち, 'one') + 俵 (ひょう, 'straw bag'), with rendaku voicing of ひょう to ぴょう.