【Disclaim】 , 【disavow】 , 【repudiate】 , 【disown】 , 【disallow】 mean to refuse to admit, accept, or approve.

【Disclaim】 implies refusal to admit or accept a claim, but it may apply specifically to a legal claim one has upon property or to a title or to the claim or imputation of something evil made by another to one's chagrin or dismay or, even more frequently, to the implied or expressed praise of oneself by another.

【Disavow】  often comes close to 【disclaim】 in meaning, but it much less often implies reference to a legal claim and fastens the attention upon a vigorous denial either of personal responsibility for something or personal acceptance or approval of something.

【Repudiate】 originally applied to a casting away of one's wife (see also 【repudiate】 under DECLINE); it may also imply a casting off or a denial of responsibility for something that has been previously acknowledged, recognized, or accepted.

【Disown】 usually stresses a repudiation or renunciation and often applies to something that has stood in close relationship to the person disowning; it may specifically imply disinheritance or abjuration.

【Disallow】 implies the withholding of sanction or approval and sometimes suggests complete rejection or condemnation.