The Collaborative International Dictionary of English v.0.48:

Fusible \Fu"si*ble\, a. [F. fusible. See Fuse, v. t.]
   CapabIe of being melted or liquefied.
   [1913 Webster]

   Fusible metal, any alloy of different metals capable of
      being easily fused, especially an alloy of five parts of
      bismuth, three of lead, and two of tin, which melts at a
      temperature below that of boiling water. --Ure.

   Fusible plug (Steam Boiler), a piece of easily fusible
      alloy, placed in one of the sheets and intended to melt
      and blow off the steam in case of low water.
      [1913 Webster]