The sexist definition in the dictionary describes a sexist as a person who shares sexist beliefs and participates in sexist behaviors. Sexist beliefs are beliefs that revolve around sexism. The word sexist can describe the nature of a comment or gesture, as well.
So how long do they typically last? Well, standard copper plugs are said to last anywhere from 10,000 to 20,000 miles (16,093 to 32,187 kilometers), while more expensive iridium or platinum spark plugs can last 60,000 miles (96,561 kilometers) or more [source: Spark plugs UK].
The first reliable spark plug was invented in 1903 by Oliver Lodge. They're aptly named as well; spark plugs are simply insulated plugs that are screwed into an internal combustion engine's cylinder head to deliver the spark that ignites the mixture of air and fuel in the combustion chamber.