Determinative; beyond dispute or question. That which is conclusive is manifest, clear, or obvious. It is a legal inference made so peremptorily that it cannot be overthrown or contradicted.
A conclusive presumption cannot be refuted; no evidence can rebut it, as in the presumption that a child who is below a certain age has a fundamental inability to consent to sexual relations.
Conclusive evidence is evidence that is either unquestionable because it is so clear and convincing or because the law precludes its contradiction. A death certificate is considered conclusive evidence that a person has died.