A straight forward motion is smooth if the right specs are present.
If there is an amount of annoying milisecond long stops constantly which cannot be measured with the FPS count, that's rather jitter.
Jitter does not equal "being not smooth"... the main difference is that you can't fight it with time based movement.
It may be caused by anything, from temporary high CPU usage of god knows what, or bad code optimization, to hardware malfunction or bad software environment.
Overall i have to say that DBPro doesn't really have its take on anything complex, at least without any plugins, it's just a standard base you can build upon from scratch by tricky coding.
-In.Dev.X: A unique heavy story based shoot'em ~35%
-CoreFleet: An underground commander unit based RTS ~15%
-TailsVSEggman: An Sonic themed RTS under development for idea presentation to Sega ~15%