n. & adj.
n. 1 the act or an instance of piping, esp. whistling or singing. 2 a thin pipelike fold used to edge hems or frills on clothing, seams on upholstery, etc. 3 ornamental lines of icing, cream, potato, etc. on a cake or other dish. 4 lengths of pipe, or a system of pipes, esp. in domestic use.
adj. (of a noise) high; whistling. piping hot very or suitably hot (esp. as required of food, water, etc.).