- In opposition or hostility to.
- In contrast or comparison with.
- In physical contact with and exerting force on.
- As a protection or defense against.
Old english ongegn "opposite, in return", from on- "on" + gegn "against".
- He is against the idea.
- Against the odds, he won.
- The wall is against the window.
- I will speak against it.
- I have nothing against him.