fib ‧ u ‧ la /ˈfɪbjələ, ˈfɪbjʊlə/ BrE AmE noun [countable] medical
[ Date: 1500-1600 ; Language: Latin ; Origin: 'piece of jewelry for fastening clothes' (because of the shape of the two bones) ]
the outer bone of the two bones in your leg below your knee