Fusible \Fu"si*ble\, a. [F. fusible. See Fuse, v. t.]

CapabIe of being melted or liquefied.

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.

Source: Webster's Revised Unabridged Dictionary (1913)