a solemn appeal to a deity, or to some revered person or thing, to witness one's determination to speak the truth, to keep a promise, etc.: to testify upon oath.
a statement or promise strengthened by such an appeal.
a formally affirmed statement or promise accepted as an equivalent of an appeal to a deity or to a revered person or thing; affirmation.
the form of words in which such a statement or promise is made.
an irreverent or blasphemous use of the name of God or anything sacred.
any profane expression; curse; swearword: He slammed the door with a muttered oath.