It should mean Godly and sacred and sacrosanct but as far as im concerned its one of those words that have been over used to the point of not really having any meaning any longer. Its been slapped on everything water and dirt to dead people.
It literally means "devoted to God" yet what it means to me on a personal level is the reverence and dedication in being of service to God. The most obvious way to be of service to God is by being of service to His children who are in need. It is through service to others that we can most fully realize what it means to be "holy."
In a secular world, the word holy has no real meaning, as all spiritual things, all supernatural things, are ignored. "Holy" means "set apart, devoted" as one sets apart the "good" dishes for Sabbath or company, or one might use the company phone only for company use. When applied to a church building, it means we see the church as set apart for worship; we don't use the church building for selling groceries or an insurance company.
I think labeling something or someone "holy" invokes immediate respect, fear, or awe from religious persons. It has shock value. "Holy" means very little to me on a personal level, but I respect others beliefs (until provoked), and try not to show disdain for their idols.