Agnostic, a.
Etymology: [Gr.
Professing ignorance; involving no dogmatic; pertaining to or involving agnosticism. -- Ag*nos"tic*al*ly, adv.
1 other Webster entry under this spelling
Agnostic, n.
One who professes ignorance, or denies that we have any knowledge, save of phenomena; one who supports agnosticism, neither affirming nor denying the existence of a personal Deity, a future life, etc.
Shades of meaning
Fernald has no entry of its own for agnostic; he lists it under skeptic.
Where he writes about it:
The atheist denies that there is a God; the deist admits the existence of God, but denies that the Christian Scriptures are a revelation from him; the agnostic denies either that we do know or that we can know whether there is a God. — from skeptic