An ignostic is one who refrains from making any judgments about "god" until a coherent definition is provided. It is often considered a subset of agnosticism and/or atheism, and is compared to theological noncognitivism. It should not be confused with agnosticism or theological noncognitivism, however.
The term "ignosticism" is a play on the words "ignorance" and "gnosticism." A direct meaning of ignosticism would mean something like, "ignorance of god(s)," meaning the ignostic doesn't know anything about gods, or doesn't know what the term "god" means. Typically the ignostic takes a position of refraining from making arguments for or against the existence of god(s) until a coherent definition of "god" is provided. Many ignostics are also theological noncognitivists, although the two positions are not mutually inclusive.
The word "ignosticism" was coined by Sherwin Wine, a rabbi and a founding figure in Humanistic Judaism.
Difference between ignosticism and agnosticism
The agnostic (and here I use Huxley's intended meaning) makes the claim that we cannot know anything about God, whereas the ignostic claims that we cannot even form an opinion of God. The difference is subtle, but distinct. The agnostic has made an opinion of God; the agnostic has a concept of God in mind and has determined that we cannot discern anything about this God. The ignostic, on the other hand, refuses to make any opinion of God in the first place, remaining ignorant until someone provides a coherent claim of God.