1) Acknowledge 2) Admit 3) Admit openly and bluntly 4) Affirm 5) Affirm as true 6) Affirm frankly 7) Assert positively 8) Avow 9) Confess 10) Declare as fact 11) Declare the provable truth 12) Declare the truth of 13) French word used in English 14) Guarantee 15) Make no bones about 16) To acknowledge deliberately 1) Affirm 2) Aver 
• (v. t.) To declare or assert positively and as matter of fact; to affirm openly. • (v. t.) To acknowledge deliberately; to admit; to confess; to sanction. • (v. t.) To appeal to; to cite or claim as authority. • (v. t.) To maintain a just or true; to vouch for. • (n.) Evidence; declaration.
A·vouch' noun Evidence; declaration. [ Obsolete] « The sensible and true avouch Of mine own eyes. Shak. » A·vouch' transitive verb [ imperfect & past participle Avouched ; present participle & verbal noun Avouching .] [ Old French avochier , Late Latin advocare to recognize the existence of a thing, to advocate, from Latin ...
avouch, avouchment 1. To declare the provable truth or validity of; to affirm: 'The father avouched that his son could not have committed the crime.' 2. To corroborate or to confirm; to vouch for: 'Was the police officer able to avouch his accusations?' 3. To accept responsibility for (an action, for example); to acknowledge. 4. To avow; to conf...
[Macbeth] (119) justify
verb admit openly and bluntly; make no bones about
to make frank acknowledgment or affirmation of; declare or assert with positiveness. · to assume responsibility for; vouch for; guarantee. · to admit; confess.