1. Solder is an alloy of different metals (usually tin and lead, sometimes silver) designed to be melted at a low temperature. typically solder is used to make contacts on an electrical circuit, but it's also used to seal plumbing pipes. however solder used for this purpose usually melts at higher temperatures.
2. a verb meaning to fuse together using solder.
1. I need to go buy some solder.
2. the pipes look like they'll need to be soldered together.