In this meaning, fused tells you that a piece of electrical equipment has a fuse in it — a small safety part whose thin wire melts and breaks the circuit if the current gets too strong. British plugs are fused: there is a little fuse inside the plug. You can say a fused plug, a fused circuit, or that a lamp is fused, meaning it is fitted with a fuse. This is mainly British electrical language. In Taiwan you are more likely to name the 保險絲 itself than to use this adjective. Though actually, in everyday British English people also say “the lights have fused” when the fuse has blown and the room goes dark. That is a stretch of the same idea: not “fitted with a fuse”, but “the fuse has given out”. Do not mix this with fused metal or fused glass, which means melted and joined together.