Source : Webster's Revised Unabridged Dictionary (1913)

Turn-buckle \Turn"-buc`kle\, n. (Mech.)
   (a) A loop or sleeve with a screw thread at one end and a
       swivel at the other, -- used for tightening a rod, stay,
       etc.
   (b) A gravitating catch, as for fastening a shutter, the end
       of a chain, or a hasp.