When a person or an outfit is fetching, they look attractive in a pleasant, almost charming way — often because the clothes, the colour, or the cut really suit them. It is a warm, slightly old-fashioned word. An older person might say “What a fetching hat,” where a younger person would say “That hat looks great on you.” It is milder than sexy: it is about looking right and pleasing to the eye, not about looking hot. You will meet it more in writing, in period films, and in the speech of older people than in teenage chat. Though actually, there is another fetching you already know: the -ing form of the verb fetch, as in fetching a book. Same spelling, different job.