oath

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A solemn, formal declaration or promise to fulfill a pledge, often calling on God, a god, or a sacred object as witness.
• noun The words or formula of such a declaration or promise.
• noun Something declared or promised.
• noun An irreverent or blasphemous use of the name of God or something held sacred.
• noun An imprecation; a curse.
• idiom (take an oath) To agree to a pledge of truthfulness or faithful performance.
• idiom (under oath) Under a burden or responsibility to speak truthfully or perform an action faithfully.

from The Century Dictionary.

• noun A solemn appeal to the Supreme Being in attestation of the truth of some statement or the binding character of some covenant, undertaking, or promise; an outward pledge that one's testimony or promise is given under an immediate sense of responsibility to God.
• noun The form of words in which such attestation is made.
• noun A light or blasphemous use of the name of the Divine Being, or of anything associated with the more sacred matters of religion, by way of appeal, imprecation, or ejaculation.
• noun Loosely — An ejaculation similar in form to an oath, but in which the name of God or of anything sacred is not used.
• noun An imprecation, differing from a curse in its less formal and more exclamatory character: it may be humorous, or even affectionate, among rude and free-living men.
• noun An exclamatory word or phrase, usually without appropriateness to the subject in hand, expressing surprise, and generally displeasure, though sometimes even approval or admiration.
• To make to take an oath; put to the oath.
• To use as an oath; swear by.
• To call, speak to, or curse with an oath.
• To swear; use oaths.

from the GNU version of the Collaborative International Dictionary of English.

• noun A solemn affirmation or declaration, made with a reverent appeal to God for the truth of what is affirmed.
• noun A solemn affirmation, connected with a sacred object, or one regarded as sacred, as the temple, the altar, the blood of Abel, the Bible, the Koran, etc.
• noun (Law) An appeal (in verification of a statement made) to a superior sanction, in such a form as exposes the party making the appeal to an indictment for perjury if the statement be false.
• noun A careless and blasphemous use of the name of the divine Being, or anything divine or sacred, by way of appeal or as a profane exclamation or ejaculation; an expression of profane swearing.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A solemn pledge or promise to a god, king, or another person, to attest to the truth of a statement or contract
• noun the affirmed statement or promise accepted as equivalent to an oath
• noun A light or insulting use of a solemn pledge or promise to a god, king or another person, to attest to the truth of a statement or contract the name of a deity in a profanity, as in swearing oaths
• noun a curse
• noun law An affirmation of the truth of a statement.
• verb archaic To pledge.
• verb Shouting out. (as in 'oathing obsenities')

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a commitment to tell the truth (especially in a court of law); to lie under oath is to become subject to prosecution for perjury
• noun a solemn promise, usually invoking a divine witness, regarding your future acts or behavior
• noun profane or obscene expression usually of surprise or anger