O

Obvious (adj.)
A successful bid or play that everyone in the room would make... except partner.

Opening Lead (n.)
Partner's first opportunity to give up a trick.

Opponent (n.)
Any of the three other people seated at the table with you. The ones seated to your left and right would like for you to do poorly, the one seated across from you knows that you will.

Overruff (v.)
The usual procedure when the doubler is behind you.