Definition of oath :
1. 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.
2. A solemn affirmation or declaration, made with a reverent appeal to God for the truth of what is affirmed.
3. 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.
4. 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.
fellow, bloke, cursing, condemnation, bad language, profane swearing, cuss, chap, imprecation, gadfly, jinx, swearword, words, denial, troth, fella, nemesis, blighter, obscenity, sworn statement, gent, torment, bane, whammy, pesterer, lad, execration, anathema, ban, pest, blasphemy, adjuration, decent, blaspheming, epithet, expletive, curse word, scourge, hex, reprobation, sacred, feller, four-letter word, affidavit, profanity
guarantee (part of speech: noun)
affirmation (part of speech: noun)
certification, promise, testimony, sanction, verification, avowal, assertion, pledge, submission, acknowledgment, validation, corroboration, proclamation, confirmation, affirmation, pronouncement, assurance, statement, endorsement, attestation, declaration, warranty, approval, admission, ratification
malediction (part of speech: noun)
promise (part of speech: noun)
promises (part of speech: noun)