What do you mean by negative acceleration? can an accelerating automobile starting from rest have a negative acceleration

The acceleration tells us how the speed changes per unit of time. If we say a body has a negative acceleration we are saying that its speed decreases over time.

If a body has a positive initial velocity and a negative acceleration: the velocity decreases. On the contrary, if the automobile has a negative initial velocity (in the opposite direction) and a negative acceleration: the velocity is increasing. Thus, an accelerating automobile starting from rest can have a negative acceleration.