But, self-identifying atheists are proud of the fact that they don't take "leaps of faith" in believing things without sufficient evidence, which would include believing that God does not exist without sufficient evidence. I think it is beneficial to make sure that the term "atheist" is defined more liberally, just as "theism" is.
And it is a fair point to say that you think the term should be defined in a liberal or broad way to be inclusive. Your reasoning-that atheists suggest they don't take leaps of faith is questionable. We all take leaps of faith.
What is sufficient evidence? Is it definite? It can hardly be definite in all cases. Sufficient include definite, but not in all cases. Otherwise we wouldn't simply call it sufficient we would use more assertive terms. Where there is not definitive proof there is usually a leap of faith. Sometimes that leap is small, other times that leap is large.
With many (strong) atheists, this leap of faith is predicated on the lack of evidence after sufficient search. (There is that word sufficient again, I need to remember to get back to that). Certainly, the absence of evidence is not definitive proof. There is always some stone unturned, some gap not filled, or some dark corner unlit. Yet, at some point we must move forward. People do this all the time. Imagine you lost your keys. You search a room, you look under the cushions, you check the table , etc. At some point you decide the key is not in that room. Do you have definitive proof? No. No matter how thoroughly you search there is always some possibility the key is in the room. But after you you are convinced that you have dwindled the possibility of the key being in the room to some level in relation to the key not being in the room, you move on.
And here, my friend, is where we find sufficient. Sufficient is the subjective amount of evidence you need to make that leap of faith. We can take a collective subjectivity in an effort to put forward some standard of sufficient. But, let's be honest, reasonable minds can disagree on many issues.