lavabo

noun5

1. •
   A washbasin, particularly (Christianity) the one in a church used in the ritual.

   • […] the […] pontiff, as he […] moved his hands […] at the Lavabo, or at the various benedictions […] — 1885
2. •
   A trough used for washing at some medieval monasteries.
3. •
   A ritual involving the washing of one's hands at a church's offertory before handling the Eucharist.
4. •
   (humorous, euphemistic) A lavatory: a room used for urination and defecation.

   • Mr. Pond fussed out and she heard the door of the little lavabo in the passage open with a loud creak. — 1930
5. •
   The small towel used to dry the priest's hands following the ritual.

   • These small liturgical towels got […] the name of Lavabo cloths or Lavaboes. — 1870