The act of serving as a master of ceremonies or hosting an event.
Present participle of emcee (from the phonetic spelling of M.C.). As entertainment and public events became more common in the 20th century, this role and its verb form became standard vocabulary.
Before radio and TV, emceeing wasn't a major career, but once those mediums exploded in the 1920s-40s, being able to say 'I was emceeing a radio show' became a common and prestigious job description.
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