I take it to mean when one is blessed by God. This blessing is made actual when we receive God's mercy and grace through his Son Jesus Christ. Since God's grace is immeasurable as in finite quantity, then it follows that this blessing is "without measure". This blessing of right relationship towards God (and humankind) is the richest and farthest reaching of any.
To be blessed so much that you cannot express/count it. Majority of people think they aren't blessed but I have read the stats and they actually tell us that most people are blessed (as in really rich even without that much money)