define wet bulb
psychrometer - a hygrometer consisting of a dry-bulb thermometer and a wet-bulb thermometer; their difference indicates the dryness of the surrounding air. dry-bulb thermometer - an ordinary thermometer with a dry bulb; used to measure the air temperature. hygrometer - measuring instrument for measuring the relative humidity of the atmosphere. wet-bulb thermometer - a thermometer with a bulb that is covered with moist muslin; used in a psychrometer to measure humidity.