An antenuptial, also known as a prenup, is an agreement made before marriage which indicates how each party would like to divide property or assets if they divorce or one party dies. Do not confuse this with a will or trust, which is an agreement made during marriage on how property or assets will be distributed when one or both parties pass.
Merriam-Webster Online Dictionary
antenuptial (adjective) - prenuptial
Synonyms:
prenup, prenuptial agreement, premarital agreement