What is the meaning of Oath?

A solemn pledge or promise that invokes a deity, a ruler, or another entity (not necessarily present) to attest the truth of a statement or sincerity of one's desire to fulfill a contract or promise.

A statement or promise which is strengthened (affirmed) by such a pledge.

A light, irreverent or insulting appeal to a deity or other entity.

A curse, a curse word.

To pledge.

Source: wiktionary.org