If a movie review describes an actor as sexy, it means he's extremely attractive and appealing. These days, this word can also be used to describe anything exciting or stylish: you might wish your old flip phone had all the sexy features of a sleek smartphone but, hey, at least you can make calls!
When a person is described as sexy, they're interesting in a romantic or arousing way. A sexy song might be incredibly romantic, made for slow dancing, or an ad might tout sexy shoes that look amazing and will be the envy of all your friends. The word sexy is often used more broadly to refer to appealing or enticing things — clothes, cars, even ideas. Before sexy was coined, around 1905, the equivalent word was sexful.