No, you have redefined it from its intended biblical purpose by superimposing man's wisdom upon it. The Bible is its own authority, man's dictionary is not - the Bible alone should be perceived as its sole dictionary. As you said, your reply was based upon a dictionary definition of a word, but one not found in the Bible. So, if you're arguing a non-biblical word by using a non-biblical source for its non-biblical validation, then technically, in a non-biblical setting alone, limited by those parameters, I guess you might be technically correct. However, that is not what matters. Instead, had you referred back to the Bible as you should have to find its truth and had not rushed to trust in man's wisdom, you would have found that according to the Bible, one can believe there is a god - but a god that is no god - one of this world - one of man's making - and due to that still be an atheist. The attributes, characteristics and glory perceived within their god is what makes that of them, because by that, in effect, they are saying there is no God.
[Rom 1:22-23 KJV]
22 Professing themselves to be wise, they became fools,
23 And changed the glory of the uncorruptible God into an image made like to corruptible man, and to birds, and fourfooted beasts, and creeping things.
[Rom 3:10-12 KJV]
10 As it is written, There is none righteous, no, not one:
11 There is none that understandeth, there is none that seeketh after God.
12 They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one.
[Psa 14:1 KJV]
1 [[To the chief Musician, [A Psalm] of David.]] The fool hath said in his heart, [There is] no God. They are corrupt, they have done abominable works, [there is] none that doeth good.