The Collaborative International Dictionary of English v.0.48:

Custodian \Cus*to"di*an\ (k?s-t?"d?-an), n. [From Custody.]
   One who has care or custody, as of some public building; a
   keeper or superintendent.
   [1913 Webster]

WordNet (r) 3.0 (2006):

custodian
    n 1: one having charge of buildings or grounds or animals [syn:
         custodian, keeper, steward]