From Longman Dictionary of Contemporary Englishgatehousegate‧house /ˈɡeɪthaʊs/ noun [countable] DHa small building next to the gate of a park or at the entrance to the land surrounding a big house
Examples from the Corpus
gatehouse• The entrance-front and gatehouse faced the town.• Fine Norman gatehouse and exhibitions on the history of the Castle.• Then, to mark the end of the service, three enormous thunder-flashes were let off in the rear gatehouse.• He's heading for the gatehouse, Marcus.• The body has been cut down and lies in the gatehouse there.• Cars would roll through the arch of the gatehouse, their headlights flashing on the ancient walls.• Whilst I was there, some one came out of the gatehouse and started walking towards me.• Curly Top hadn't had enough time to get more people to the gatehouse. 