0 a woman who is not a member of the clergy (= religious leaders, especially Christian priests, ministers, etc.) but who belongs to a religious group, especially a group living together in a convent, and who does simple work for the group, such as preparing food:
The bread and cheese was brought up on a platter by an aged lay sister.
Only one of the lay sisters who served at Kerever Park was still alive.
She became a lay sister to make “expiation” for the scandals of her family.
