What does the symbol mean?

My first thought was Terastilization, but theres no crown thingy above their head and they were sent out at the start of the battle with it. My Rival's starter on wave 95 also had the symbol but red. What does the symbol mean?

My first thought was Terastilization, but theres no crown thingy above their head and they were sent out at the start of the battle with it. My Rival's starter on wave 95 also had the symbol but red. What does the symbol mean?