I would venture to say that the overwhelming majority of atheists would define their position as weak atheism - lack of belief in god.

According to the data we have on this 13.6% of people think 'atheism' means "a person who lacks a belief in God or gods" while 79.3% think it means "a person who is convinced that there is no God or gods" or "a person who believes there is no God or gods." (Bullivant 2008, "Research Note: Sociology and the Study of Religion", Journal of Contemporary Religion 23[3]). So the preference is pretty overwhelmingly in the opposite direction.

Granted, this was 2008, but I don't think there's any reason to think attitudes have changed.