Turn-buckle \Turn"-buc`kle\ (t[^u]rn"b[u^]k`k'l), 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.
[1913 Webster]