Definition of "engager" [en•ga•ger]

• One who, or that which, engages. (noun)
• One who enters into an engagement or agreement; a surety. (noun)

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• "For example, Twitter usage shows that a few companies play the role of engager -- making an entire community feel like they are part of a group that just clicks."
• "The bulk of Micromet's drug research relies on what it calls "BiTE antibody technology," for Bi-specific T cell engager."
• "Even Senator John Kerry, a serial Assad engager, says he no longer believes the dictator."