What is mustio? mustio is mustioWhat is mustio? adj. Melancólico, triste: lleva todo el día mustio.adj. melancholic, sad: leads throughout the day faded.Lánguido, marchito: la planta está mustia.Languid, withered: the plant is mustia.tr. y prnl. marchitar.♦ Se conj. como cambiar .tr. and prnl. wither. ♦ is conj. How to change.