An "agnostic" is a person who does not believe there is enough evidence to know whether god exists. it is unknowable to that person.

An aqnostic believes that there is not enough evidence to prove the existence of god. They do not however deny the existence of god and believe that there is a possibility god does exist but until they have seen proof for themselves they will not accept that god exists. They are what are know as skeptics but are open minded to the possibility of god.