Definition of "reformer"

One who reforms, or who works for reform.  examples

(historical, Christianity) One who was involved in the Reformation.

(chemical engineering, fuel cells) A device which converts hydrocarbons into a hydrogen-rich mixture of gases.  examples

(petrochemistry) A device used to convert petroleum refinery naphthas, typically having low octane ratings, into high-octane liquid products called reformates.  examples