1) The action of a creeper, stalker, pervert, etc., but taken to a much more intimate level.
2) An action between two people, usually a formal couple, friends with benefits, etc., where one tends to initialize the sexual mood/tension for the other person, or simply to turn someone on. It can be done physically (like caressing or fondling), verbally (like an innuendo
), etc. It can occur anywhere at any time—neither time nor privacy is taken into consideration at times. Similar to foreplay
3) Making something (phrase, object, action, etc) have a second, more sexual meaning.
Adapted from the Italian word "bruto", which means bestiality. In Italy, a bruto is colloquial for a person with a strong, “beast-like” sexual appetite.