Aesthetic Adept (3.5e Feat)
From D&D Wiki
Benefit: Your Monk and Warblade levels stack for the purpose of determining your unarmed strike damage and flurry of blows ability, as well as your AC bonus, which becomes dependent on your INT score. In addition, you can multiclass freely between the Monk and Warblade classes.
Normal: Your Monk and Warblade levels do not stack for these purposes, and once you multiclass out of monk, you cannot reenter the class.