wet-bulb thermometer n 1: a thermometer with a bulb that is covered with moist muslin; used in a psychrometer to measure humidity [ant: {dry-bulb thermometer}]
Wet-bulb thermometer \Wet-bulb thermometer\ (Physics) That one of the two similar thermometers of a psychrometer the bulb of which is moistened; also, the entire instrument. [Webster 1913 Suppl.]