girth  
noun uk/ɡɜːθ/ us/ɡɝːθ/
  (MEASUREMENT)      
  [ C or U ]围长;干围;腰围 
the distance around the outside of a thick or fat object, like a tree or a body
  The oak was two metres in girth. 这棵橡树干围长两米。 
humorous His ample girth was evidence of his love of good food. 他那粗大的腰身表明他极其贪吃。 
   (HORSE EQUIPMENT)      
 [ C ](固定马鞍或鞍上货物的)肚带 
the strap that goes around the middle of a horse to keep the saddle (= rider's seat) or the load in the right position
  Loosen the girth a little. 把马的肚带松一松。