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Webster 1913 Edition

Adj.

[Pref.

post-

nuptial

Being or happening after marriage;

as, a

postnuptial

settlement on a wife

Kent.

Adj.

[post and nuptial.] Being or happening after marriage; as a postnuptial settlement on a wife.

postnuptial ‎(not comparable)

Subsequent to marriage.
They made a postnuptial agreement regarding their bank account.