Definition of Anteroposterior (AP)
Anteroposterior (AP): In anatomy, AP stands for anteroposterior: from front-to-back. For example, an AP X-ray of the chest is taken from front-to-back.
AP in this respect is the opposite of PA, which stands for posteroanterior: from back-to-front.Source: MedTerms™ Medical Dictionary
Last Editorial Review: 6/14/2012