v.1. To place something so that it is touching something on the side: I set my golf clubs against the car and opened the trunk.
2. To place something against some background: The author has set the love story against the backdrop of war. In the picture, the old church is set against the large, glass skyscrapers.
3. To place something in contrast to something else: The price seems like a bargain when you set it against real estate prices in larger cities.
4. To incite someone to oppose or resist someone or something: The civil war set families against one another. The bosses are set against the proposal, so I doubt it will go through.