upon
preposition
°Being above and in contact with another.
"Place the book upon the table."
°Being directly supported by another.
"The crew set sail upon the sea."
verb
°Being the target of an action.
"He was set upon by the agitated dogs"
°Incidental to a specified point in time or order of action; usually combined with here-, there- or where-.
"The clock struck noon, whereupon the students proceeded to lunch."
synonyms: on