Cyano's correct, it's velocity.

One easy way to look at it is that integrals (area under the curve) are basically multiplication. I mean, when you write an integral for this, it's [itegral sign]a(t)*dt. So, it's really just acceleration * time which equals velocity.

On the other hand, derivatives are division. So the derivative of velocity with respect to time is velocity/time = acceleration. Again, dv/dt shows this pretty well.