a. a sanitary installation for receiving and disposing of urine and faeces, consisting of a bowl fitted with a water-flushing device and connected to a drain
b. a room containing such an installation
2.
the washing place in a convent or monastic establishment
[C14: from Late Latin lavātōrium, from Latin lavāre to wash]
late 14c., "washbasin," from L. lavatorium "place for washing," noun use of neut. of adj. lavatorius "pertaining to washing," from lavatus, pp. of lavare "to wash" (see lave). Sense of "washroom" is first attested 1650s; as a euphemism for "toilet, W.C.," it is attested from 1924.