em·bay·ment \ə̇mˈbāmənt, em-\noun (-s) 1. a.: formation of a bay (as by depression of the land about a river mouth so that the sea overflows it) — compare estuary 1 b.: a bay or a conformation resembling a bay 2.: an irregular corrosion of a crystal by the magma in which it occurs as a foreign inclusion or as by previously crystallized mineral