Of a house: joined to another one on one side, having one shared wall.
In the smaller plans of a "Mansionette near Wimbledon Park," "Semi-detached Houses," and "The Compact House built near Blackheath," we are not favoured with any scale.1860 July 23, The Gentleman's Magazine, page 80:
The murderer should be a little man of the professional class — a dentist or a solicitor, say — living an intensely respectable life somewhere in the suburbs, and preferably in a semi-detached house, which will allow the neighbours to hear suspicious sounds through the wall.1946, George Orwell, Decline of the English Murder: