Source : Webster's Revised Unabridged Dictionary (1913)

Janitor \Jan"i*tor\, n. [L., fr. janua a door.]
   A door-keeper; a porter; one who has the care of a public
   building, or a building occupied for offices, suites of
   rooms, etc.

Source : WordNet®

janitor
     n : someone employed to clean and maintain a building