What is Adulterium?

Legal Definition
In the old records this word does not signify the offence of adultery, but the fine imposed for its commission. Barr. on the Stat. 62, note.
-- Bouviers Law Dictionary
Legal Definition
A fine anciently Imposed as a punishment for the commission of adultery.
-- Black's Law Dictionary
Legal Definition
A fine imposed for adultery.
-- Ballentine's Law Dictionary