onus UK /ˈəʊnəs/US /ˈoʊnəs/ noun5 •A legal obligation.The onus is on the landlord to make sure the walls are protected from mildew. •Burden of proof, onus probandi. •Responsibility; burden.The onus is on those who disagree with my proposal to explain why.The onus is on you to make the first move. •Blame.He'll always bear the onus of having caused the accident. •Stigma.Geraldine evades the onus of ambition by subordinating it to the service of her family, and escapes the onus of sexuality by bodily mutilation — 1993 formsonera · onuses