A device used to detonate an explosive device etc.
a small explosive device attached to the railhead to provide an audible warning when a train passes over it.
A small cylinder of some other material of the same function in a cigarette lighter, etc.
A piece of flint, such as a gunflint, used to produce a spark by striking it with a firestriker.
A type of maize/corn with a hard outer hull.
A hard, fine-grained quartz that fractures conchoidally and generates sparks when struck against a material such as steel, because tiny chips of the steel are heated to incandescence and burn in air.
Anything figuratively hard.
To furnish or decorate an object with flint.