Disavow, v. t. [imp. & p. p. Disavowed; p. pr. & vb. n. Disavowing.]
Etymology: [F. désavouer; pref. dés- (L. dis-) + avouer to avow. See Avow, and cf. Disavouch.]
1. To refuse strongly and solemnly to own or acknowledge; to deny responsibility for, approbation of, an the like; to disclaim; to disown; as, he was charged with embezzlement, but he disavows the crime. A solemn promise made and disavowed. Dryden.
2. To deny; to show the contrary of; to disprove. Yet can they never Toss into air the freedom of my birth, Or disavow my blood Plantagenet's. Ford.
Shades of meaning
Fernald has no entry of its own for disavow; he lists it under renounce.
Where he writes about it:
A person may deny, disavow, disclaim, disown what has been truly or falsely imputed to him or supposed to be his. — from renounce
He may deny his signature, disavow the act of his agent, disown his child; he may repudiate a just claim or a base suggestion. — from renounce