There are several ways of defining the term "lave." Its most common meaning is to wash or bathe something, though it may also refer to the way a body of water flows and "washes up" on the shore. Dictionary.com also lists that it can mean to ladle something, but this is not used in modern English.
You might be familiar with the term "lave" as a root of the word "lavatory." While it is an older term for referring to the washroom or toilet room, one can still encounter it in public spaces and more formal settings. In England, students must ask for the "lavatory pass" in order to take a trip to the bathroom. And what does one do in the lavatory? Among other things, lave the hands!