authenticate UK /ɒˈθɛn.tɪ.keɪt/US /ɔˈθɛn.tɪ.keɪt/verb 2adjective 1forms 3 verb2 •To prove authentic; to determine as real and true.He didn’t manage to authenticate the portrait: it’s probably a fake.The server could not authenticate the request. •To render authentic; to give authority to, by the proof, attestation, or formalities required by law, or sufficient to entitle to credit. adjective1 •Synonym of authentic. formsauthenticated · authenticating · authenticates