Looking or feeling like wax. You use it for a surface that is smooth, a little soft, slightly shiny in a dull way, and not quite alive-looking. The most common use is about skin: a sick person's face can look waxy — pale, smooth, and somehow not real, like a candle. Writers use it about dead bodies too, so the word can carry a small chill. It also works for real things made of wax or covered in wax: a waxy coating on an apple or a lemon, waxy leaves on some plants that keep water in, the waxy layer inside a paper cup. And it describes how something feels between your fingers — a waxy cheese, a waxy lipstick, a waxy potato that stays firm when you boil it and does not go floury. That last one is a real cooking word in English: potatoes are sold as 'waxy' or 'floury', and the two behave differently in a pot. So the word runs from a plain physical description (this is like wax) to a quiet judgement about a person's health (this face looks wrong). Nothing about it is formal; anyone can say it.