Passive aggression to me means some one bullying others to get their own way all the time, not by violence and shouting but by manipulating other people in non-aggressive ways. The most common way is emotional blackmail.
In my flat sharing days I had a flat mate who, whenever anyone wanted to do something she didn't want to do, have some friends round to the flat or cook something they liked and she wasn't keen on, would look down in the mouth and say she had a headache and didn't feel up to it. If you still insisted on having friends round she would mooch around in her dressing gown saying how ill she was, making everyone feel uncomfortable so that they went home early. If she didnt like supper, she would never let anyone cook her anything else but would sit there looking sad and nibbling cream crackers.
My paternal GM had a good line in it. She didn't like my DM and on the day my parents officially announced their engagement it was decided that they would have a celebration lunch with DM's parents and then go to tea with DF's parents, except when they got round to the house for tea, they were greeted by my GF, on his own, as GM had a bad headache and had gone to bed for the afternoon. The celebration tea was tea and a biscuit in the kitchen by themselves because GF was upstairs caring for his wife.
You often read cases of this kind of behaviour on threads on Gransnet, elderly mothers, who manipulate daughters by suggesting they neglect them, daughters limiting grandparents access to grandchildren. No violence, no shouting just quietly making other peoples lives miserable so that the bully can triumph.