Re: For a rocket, surely the correct term should be 'escape acceleration'?

First of all, I'll defer to other online sources for wording of the definition and examples of how to compute escape velocity.

I concur with the paragraph at Wikipedia distinguishing velocity from speed. This is really a speed. A velocity specifies a speed and a direction.

I see two reasons why acceleration isn't used.

First and fundamentally, the problem is one of energy: how much energy does it take for an object to escape from Earth. Kinetic energy is a function of speed, so we end up with something we'd call escape speed or escape velocity. See also these articles from ThinkQuest and Univ. of Oregon and Hypertextbook.

Secondly, even if you were looking at this from the perspective of "I'm going to continually accelerate my object so as to overcome gravity", you still don't know the minimum effort required to escape Earth. You could've applied an equivalent energy (less, in fact) in a short burst, earlier in the process and glided out of Earth's gravity well.

In summary, the answer to your question is "no". The 'escape acceleration' would not be a useful term or concept. The problem centers around energy and kinetic energy is not about acceleration, it's about the speed you end up at. Did you require acceleration to reach that speed? certainly. But, the kinetic energy of the escape speed is irrespective of what sort of acceleration you used. That type of generality is incredibly useful, esp. in engineering. You may evaluate a whole host of propulsion concepts based on how well they achieve escape velocity.

Hope that helps,

Troy.