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: --
She became a lay sister to make “expiation” for the scandals of her family.
Only one of the lay sisters who served at Kerever Park was still alive.
The bread and cheese was brought up on a platter by an aged lay sister.