What does "uncreated God" mean?

I often hear references to the "uncreated God", citing passages such as Psalm 90:2 "from everlasting to everlasting you are God". What is the specific meaning of the word "create" in the above phrase, according to various denominations that employ it (or attempt to refute it)? What is an overview of doctrines held by the various denominations about the meaning of this phrase? Does the word "create" in this context have an unambiguous, rigorous and identifiable meaning according to such doctrines, or is it assumed the hearer automatically knows what specifically it is and isn't intended to mean? What is that meaning? Bonus: How does this relate to the meaning of the word "create" used in Genesis 1:1?