Friend (orignally military) (From "Opposite Number")

A stupid person; it refers to the lack of surface area on an individual's brain. The general thought is that the more surface area (wrinkles, creases, etc.) a brain has, the smarter the person is. Conversely, a person with a smooth brain (no wrinkles) has less surface area and would therefore be stupid.

Opposition research; otherwise known as digging up dirt on a political opponent.

opposite lock, informally for opposite lock. A corrective step in controling over-steer in car. Act of turning the steering wheel, in the opposite direction of tail slide.

from the meaning "opportunity school" - a place where spastics or underachievers are sent to get them out of the mainstream education system.

Short for operations. Used when going to a party where people will be getting hammered and you have to be very low key.

In baseball,when you hit the ball to the opposite field.