The Collaborative International Dictionary of English v.0.48:

Catgut \Cat"gut`\, n. [Cat + gut.]
   1. A cord of great toughness made from the intestines of
      animals, esp. of sheep, used for strings of musical
      instruments, etc.
      [1913 Webster]

   2. A sort of linen or canvas, with wide interstices.
      [1913 Webster]

WordNet (r) 3.0 (2006):

catgut
    n 1: perennial subshrub of eastern North America having downy
         leaves yellowish and rose flowers and; source of rotenone
         [syn: catgut, goat's rue, wild sweet pea, Tephrosia
         virginiana]
    2: a strong cord made from the intestines of sheep and used in
       surgery [syn: catgut, gut]