How do killer whales play?

Yes, orcas like to play. Killer whales are very social animals, forming family and friendship bonds that remain throughout their lives. Play and social behavoirs are often observed in the well studied populations, such as the southern and northern residents in Washington state and British Columbia.

The Center for Whale Research lists playful activities:

Breaching. Leap, twist in the air and land on their sides or backs (requiring an exit speed of 40 km/hr). Spyhopping. Rise vertically above the water surface to look around, showing their white bellies up to their pectoral fins. Pec or Fluke Slaps, and Lobtailing. Repeatedly splash the water surface with their pectoral fins or just slap the surface with their tails.