That one of the two similar thermometers of a psychrometer the bulb of which is moistened; also, the entire instrument.
Thermometer on a psychrometer that has a moisten wick on its reservoir bulb. When ventilated this thermometer records a temperature that is modified by the cooling effects of evaporation. This measurement and the temperature reading from a dry-bulb thermometer are then used to determine the air's relative humidity or dew point from a psychrometric table.
In a psychrometer, the thermometer that has the wet, muslin-covered bulb, and, therefore measures wet-bulb temperature.