Moving around in public generally in a vehicle, though this can be accomplished on foot, with the sole purpose of interfering with rude white people and truck bros who are being crappy to other humans just because they can.
The term is based on practices of the Orca Whale (Killer Whale), which seeks out the Great White sharks to toy with and regulate.
While the Orca will end the Great White and consume its liver, playing orca only requires the regulation of the great white Karens of the world.
Like the orca hunts a shark, humans playing orca will seek out the great white of Karens (generally the male subspecies) and keep them occupied by any means so others may move about in public unbothered by the great white Karen.
"For the truck bros, I'm the super fast, raging Prius driver here to play orca to their great white."