The Collaborative International Dictionary of English v.0.48:

Service entrance \Serv"ice entrance\
   an entrance for use of servants and those providing services,
   such as deliveries or repair work.
   [PJC]

WordNet (r) 3.0 (2006):

service entrance
    n 1: an entrance intended for the use of servants or for
         delivery of goods and removal of refuse [syn: service
         door, service entrance, servant's entrance]