Noun
One who, or that which, engages.
engagers in conflicts
(biochemistry) A particle or compound which engages certain cells in a process.
One who enters into an engagement or agreement; a surety.
Source: en.wiktionary.orgDisillusioned by the Covenanters, in October Charles attempted to escape from them and rode north to join with an Engager force, an event which became known as "the Start", but within two days the Presbyterians had caught up with and recovered him. Source: Internet