fuse

Etymology 1

From Italian fuso and French fusée, from Latin fūsus (“spindle”).

noun

1. A cord that, when lit, conveys the fire to some explosive device.
   The Government, having lit the fuse, is not going to be allowed to flee the explosion. 1962 October, “Talking of Trains: Passed to you, Mr. Macmillan”, in Modern Railways, page 220
2. (manufacturing, mining, military) The mechanism that ignites the charge in an explosive device; a detonator.
3. (figurative) A tendency to lose one's temper.
   When talking about being laid off, he has a short fuse.
4. A friction match for smokers' use, having a bulbous head which when ignited is not easily blown out even in a gale of wind.
5. A kind of match made of paper impregnated with niter and having the usual igniting tip.

verb

1. To furnish with or install a fuse to (an explosive device) (see Usage notes for noun above).

Etymology 2

Back-formation from fusion (“to melt”), first to verbal sense, then noun.

noun

1. (electrical engineering) A device to prevent excessive overcurrent from overload or short circuit in an electrical circuit, containing a component that melts and interrupts the current when too high a load is passed through it.

verb

1. (transitive) To liquify by heat; melt.
   Pure sodium is a lustrous metal... it fuses very easily at a temperature of 97°, and distils at a bright red heat (742°...) 1891, Dmitri Mendeleev, The Principles of Chemistry (1905) 3rd edition, Vol. 2, p.553, Tr. George Kamensky, of Основы химии (1867)
2. (transitive) To melt together; to blend; to mix indistinguishably.
   Actually the New York, New Haven and Hartford, Boston & Maine, Maine Central, Bangor & Aroostook and Rutland Railroads already are doing so; if they are fused, they would have a combined route mileage of 5,269 and assets totalling £318 million, …. 1960 January, “Talking of Trains: N.& W.-Virginian merger”, in Trains Illustrated, page 9
3. (intransitive) To melt together.
4. (transitive, electricity) To furnish with or install a fuse to protect a circuit against overcurrent.
5. (transitive, electricity, of a circuit) To have been protected against overcurrent by its fuse melting away, creating a gap in the wire, thus stopping the circuit from operating.
   When the bath overflowed, the downstairs lights fused, so we need a torch.
6. (organic chemistry) To form a bicyclic compound from two similar or different types of ring such that two or more atoms are shared between the resulting rings