If someone looks gaunt, they look very thin, usually because they have been very ill or worried. Looking gaunt and tired, he denied there was anything to worry about. = drawn
very thin especially from disease or hunger or cold; "emaciated bony hands"; "a nightmare population of gaunt men and skeletal boys"; "eyes were haggard and cavernous"; "small pinched faces"; "kept life in his wasted frame only by grim concentration"
If you describe a building as gaunt, you mean it is very plain and unattractive. Above on the hillside was a large, gaunt, grey house