The Oxford Thesaurus An A-Z Dictionary of Synonyms - girth n.

1) circumference, perimeter, ambit, periphery, circuit: His girth steadily expanded as he approached fifty. 2) belt, girdle, border, cincture, waistband, cestus, cummerbund, Archaic zone, US and Canadian cinch: Tighten that girth or the saddle will come off.