what is a passive aggressive

ok well, today at work someone asked me what is a passive aggressive individual. It seems that in my line of work I come accross patients who may be acting in an aggressive way or in a passive aggressive way because that is part of their symptoms and it is my job at their threapist to try to change that behavior. There are staff who are also passive aggressive. so the definition of someone who is aggressive but in a passive way would be someone who smiles in your face and acts like a friend and then causes you to get in trouble or will block your car in the parking lot so that it will take you a long time to get out all the while saying " oh, I'm sorry I didnt realize i was blocking you ". passive aggressive people hide their true anger and aggression and leave only little clues to their true self. The aggressive person will tell it to your face when they dont like you and are upfront where as the passive type will seem like a friend but will hurt you in the end. Most of the time the passive aggressive person will bottle their anger up until it explodes. the aggression will have to come out some how like a boiling tea kettle.