/ gɜːθ; NAmE gɜːrθ/ noun
1.
[ U , C ] the measurement around sth, especially a person's waist :
a man of enormous girth
a tree one metre in girth / with a girth of one metre
2.
[ C ] a narrow piece of leather or cloth that is fastened around the middle of a horse to keep the seat, (called a saddle ), or a load in place
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WORD ORIGIN
Middle English (in sense 2): from Old Norse gjo̧rth .