flatmate

Etymology

From flat + -mate.

noun

1. A person with whom one shares a flat.
   Yet when both Regine and her flatmate are at home they tend to spend their time in their rooms, although Regine (and probably the flatmate too) tends to spend more time in the communal areas of the flat when the other is not at home. 2002, Elaine Lally, At Home with Computers, page 149
   So, it would probably [be] best if we could find another flatmate and go for a flat of five, and if old Chip does pull out, at least we can then drop down to a flat of four. What do you reckon? 2007, C. N. Barton, The Cambridge Diaries: A Tale of Friendship, Love and Economics, page 121
   Kamal moved Fathi′s things into his own room, and the two became flatmates. The apartment in which Kamal lived was spacious, with several large rooms and various flatmates. 2011, Ghada Osman, A Journey in Islamic Thought: The Life of Fathi Osman, page 63
2. (UK, Ireland, New Zealand) A person with whom one shares any rental dwelling, not necessarily a flat.
   It had been weeks since all the flatmates had sat down together for a meal. Communication was breaking down. Written notes had begun to appear all over the house; please don′t touch this food, I bought it especially for Hermione[…]. 1993, Beryl Fletcher, The Iron Mouth, page 190
   One night, one of the flatmates (the one who owned the house) was ranting and raving all night about her girlfriend. 2003, Jen Birch, Congratulations! It′s Asperger Syndrome, page 51
   The position may have been different when your client was living in the house with the flatmates. 2007, CCH New Zealand, Top 100 Questions and Answers on Taxing Land Transactions, page 97