Full entitlement means you do not have an active VA loan and can use your full benefits when applying for a mortgage. You can have full entitlement if you've never used your loan benefit before, if you've paid off a previous VA loan and sold the house, or you've repaid the VA in full after a foreclosure or short sale.
When you have your full entitlement, your Certificate of Eligibility (COE) will say, "This Veteran's basic entitlement is $36,000." When you have used your full entitlement, your COE will say, "This Veteran's basic entitlement is $0."