dormer
Concise Oxford English Dictionary © 2008 Oxford University Press:
dormer /ˈdɔːmə/ (also dormer window)
▶noun a window that projects vertically from a sloping roof.
– origin C16 (denoting a dormitory or bedroom window): from OFr. dormeor ‘dormitory’, from dormir ‘to sleep’.
'dormer' also found in these Oxford entries:

