kneeboard

Short definition from Wiktionary

Noun

1. 1
   A short (often less than 6'), broad (sometimes extremely broad) surfboard designed to be ridden in the surf in a kneeling position, and often having traction pads in the central area as an alternative to wax, to help the knees grip the deck.
2. 2
   A clipboard carried in the lap of an airplane pilot, on which basic flight data is recorded.
3. 3
   A short wakeboard designed to be ridden in the kneeling position.

Verb

1. 1
   to surf or water-ski using a kneeboard