I've heard this term repeatedly used in context of strafing as well as landing shots. What does it mean in terms of Counter Strike, and why is it so controversial?
I did some research on this matter because i was very curious about it when you posted this question and i finally found what adada is.
ADADADADA is pressing A and D keys to strafe left and right while you're shooting. It makes you harder to hit (since you're moving left and right constantly enemies will miss you more often then they would if you were standing still), but strafing left and right doesn't really reduce your accuracy by much, it's almost the same as if you were shooting while standing still.
That taken into account, a lot of people are saying ADADA is abuse since you're just as accurate and you're harder to hit.