Solid Propellant Missile From A Submarine or Surface Ship

If it wasn't a missile that's news to at least one expert, as related here:

Doug Richardson, the editor of Jane’s Missiles and Rockets, examined the video for the Times of London and said he was left with little doubt. 

"It’s a solid propellant missile," he told the Times. "You can tell from the efflux [smoke]." 

Richardson said it could have been a ballistic missile launched from a submarine or an interceptor, the defensive anti-missile weapon used by Navy surface ships.