A distiller is a person whose work is to make strong alcoholic drinks — whisky, rum, gin, brandy — by heating a liquid so the alcohol rises as steam and then cooling that steam back into a stronger drink. The same word also names the company that does this. You will see it on bottle labels and in news about drinks: “a small island distiller,” “an independent distiller.” It is an ordinary word in that world, not slang and not especially fancy. People do not use it for someone who makes beer (that person is a brewer) or wine (a winemaker). There is also a quieter sense: a distiller can be the machine itself, the still that boils and cools the liquid, including a water distiller in a lab or kitchen. In everyday talk, though, if someone says distiller they almost always mean the drinks maker, person or firm.