noun

• (originally US, water sports) A board on which a person stands to ride for leisure which is pulled on a water surface by a motorboat.
  "At high tide in the afternoon I watched his guests diving from the tower of his raft, or taking the sun on the hot sand of his beach while his two motor-boats slit the waters of the Sound, drawing aquaplanes over cataracts of foam."

verb

• (sports, intransitive) To ride for leisure standing up on a board pulled on a water surface by a motorboat.
  "She waved her arm—a significant and imperative signal—but she realised, almost as she did it, that there was scant chance of any one aquaplaning at thirty or forty kilometres an hour looking to the right or to the left."
• (by extension, chiefly British, automotive) Of a car or other road vehicle: to lose traction with the road due to the vehicle's tyres sliding on a film of water on the road.
  "So much water. They were held up by it, the tyres skating over a film of rain. Aquaplaning. Flying his sister’s fancy car through the wet air. Touching nothing."