A Hyper-Turbo event is one in which the blind levels increase extremely quickly even faster than in a Turbo tournament. The length of each round (before the blinds/antes increase) in a Hyper-Turbo tournament is usually 3 minutes.
A typical standard online tournament blind structure increases every 10-20 minutes. The actual speed depends on a number of factors including the tournament's buy-in. Turbo blind structures tend to increase every five or so minutes, with hyper-turbos being even crazier, raising the blinds every three-minutes or so.