1. adjective /ˈɒpəzɪt,ˈɑpəsɪt/
a) located directly across from something else, or from each other

She saw him walking on the opposite side of the road.

b) facing in the other direction

They were moving in opposite directions.

2. noun /ˈɒpəzɪt,ˈɑpəsɪt/
a) something opposite or contrary to another

"Up" is the opposite of "down".

b) an opponent
3. adverb /ˈɒpəzɪt,ˈɑpəsɪt/
In an opposite position.

I was on my seat and she stood opposite.

4. preposition /ˈɒpəzɪt,ˈɑpəsɪt/
a) facing, or across from

He lives opposite the pub.

b) in a complementary role to

He played opposite Marilyn Monroe.

Wikipedia foundation.