1. Not known or that which is unknown; an assertion of the uncertainty of all claims to knowledge: The word agnostic was invented, or coined, by T.H. Huxley, the eminent British biologist, in his Science and Christian Tradition, published in 1870, page 21; because he felt that the existence of God was a proposition that could not be proven scientifically. So an agnostic says, in effect, "There may be a God, but as for me, I do not know."
2. A person who believes that the existence of God is unknown, but does not deny the possibility that God exists: Sherman, who was an agnostic, was not convinced that there is a God; however, he also was open to considering any evidence that would prove that God is a reality.
3. Someone who thinks it is impossible to know whether there is a God, future life, or anything beyond the material phenomena we are experiencing and who is unwilling to accept supernatural revelation: One dictionary defines an agnostic as being someone who is not, as is often held, someone who doesn’t know whether there is a God, but a person who believes it is impossible to know or to prove anything about the existence of God.

The inability to complete a bodily movement because of a failure to recognize and to interpret sensory information upon which its performance depends: "The player attempted to swing the baseball bat and hit the baseball but was unable to do so because she experienced agnostic apraxia and could not perceive how close the ball was to her."