Litteraly meaning a lack of claim to knowlege. Generaly is refering to a lack of claim to knowelge about the possible existance of god(s).
One can be an agnostic theist. Meaning that while they personally believe in a god they are open to the idea that they could be wrong. Or an agnostic atheist who personally believes there is no god(s) but also admits they have no real way of knowing the truth.
The term agnostic is ment to be used in conjunction with the words theist or atheist but will often be used as a stand alone deffinition of ones beliefs. Agnostic's will often be split in the middle of these two phiolsophys.
Is the opposite of gnostic- meaning a claim to knowlege.
Agnostic person: "I don't think its possible to tell if there is or isn't a god but I respect your beliefs as long as your not murdering or raping people as part of them."
Other agnostic person: "We will find out the truth on this issue when we are dead and I would not care to die sooner just to find the answer."