to treat as common what is holy: to profane, defile, or strip of its sacred standing
This is the most common use of the word and the one that carries the most weight in the Bible. Something or someone set apart for God (the Sabbath, the sanctuary, God's name, the priesthood, a person) is dragged back down to ordinary status, robbed of the special standing that made it holy. The opposite of this word is to keep something holy.
The word covers a wide spread of objects. People profane God's name when they swear falsely by it or live in a way that drags it through the mud. The Sabbath is profaned when it is worked like any other day. The sanctuary and its offerings are profaned when they are touched, used, or approached in ways that ignore their holiness. A priest could profane himself or his daughter. Even a person's own dignity or marriage bed can be profaned.
In one specific legal use, the word means to put a new vineyard to common use for the first time, that is, to enjoy its fruit after the years in which it was off limits. The idea is the same: what was held back from ordinary use is now brought into it.