What is same as Velum, 3. To take the veil (Eccl.), to receive or be covered with, a veil, as a nun, in token of retirement from the world; to become a nun called?

veil — (Zoöl.) Same as Velum, 3. To take the veil (Eccl.), to receive or be covered with, a veil, as a nun, in token of retirement from the world; to become a nun. (Webster's 1913.)

Sources