Something opposite or contrary to something else.

An opponent.

An antonym.

“"Up" is the opposite of "down".”

Located directly across from something else, or from each other.

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

Of leaves and flowers, positioned directly across from each other on a stem.

Facing in the other direction.

“They were moving in opposite directions.”

In an opposite position.

“I was on my seat and she stood opposite.”

Facing, or across from.

“He lives opposite the pub.”

In a complementary role to.

“He played opposite Marilyn Monroe.”

On another channel at the same time.

“The game show Just Men! aired opposite The Young and the Restless on CBS.”