agnosticism

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The doctrine that certainty about first principles or absolute truth is unattainable and that only perceptual phenomena are objects of exact knowledge.
• noun The belief that the existence or nonexistence of a deity or deities cannot be known with certainty.

from The Century Dictionary.

• noun The doctrines of the agnostics; the doctrine that the ultimate cause and the essential nature of tilings are unknowable, or at least unknown.
• noun Belief in the doctrines of the agnostics.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Theol.) That doctrine which, professing ignorance, neither asserts nor denies.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The view that absolute truth or ultimate certainty is unattainable, especially regarding knowledge not based on experience or perceivable phenomena.
• noun The view that the existence of God or of all deities is unknown, unknowable, unproven, or unprovable.
• noun Doubt, uncertainty, or scepticism regarding the existence of a god or gods.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the disbelief in any claims of ultimate knowledge
• noun a religious orientation of doubt; a denial of ultimate knowledge of the existence of God