In this list this means a form of Fortified Manor House where all the accommodation, including the hall, is in one tower, often with a parapet along the top of the tower, turrets and other defensive features. Although the residential buildings form one tower there would usually have been a court of ancillary buildings often with a defensible walled enclosure (sometimes called a barmekin or bawn). In England and Wales these were high status buildings, usually of baronial or greater status. Unsurprisingly for high status buildings, inhabited by lords, these sites are often named 'castle'.
This form of integral accomodation block was common in Scotland and Ireland but relativel rare in England and Wales.
N.B. The term 'towerhouse' is much used and loosely defined, many authors use it for any type of defensible house, including pele towers or even bastles, and there is, indeed, a continuum in size and status between these buildings which can be used to justify that practice.