an underground room or vault, esp. beneath a church
Origin of undercroftMiddle English ; from under- (see under-) + croft, a vault ; from Medieval Latin crupta ; from Classical Latin crypta, crypt
A crypt, especially one used for burial under a church.
Origin of undercroftMiddle English : under-, under- + croft, crypt (from Middle Dutch crofte, from Medieval Latin crupta, from Latin crypta, crypt; see crypt).