Types of calls
An overcall is the second or subsequent call of a bet.
Then C has overcalled. The overcall of C might indicate more strength than the call
Cold call means calling a raise when you hadn't called the initial bet earlier in the betting round.
If the betting goes
Then D has made a cold call, A and B did not cold call.
In most cases you should worry about D's hand more than A's or B's and
maybe even more than C's hand.
Smooth call and Flat call
They pretty much mean the same thing.
Flat call is probably used more often used when you're just
trying to describe what happened.
Smooth call is probably used more often when you're trying to describe
how smart and tricky you are. When you hear somebody use the term smooth call you might want to start looking for signs of FPS (Fancy Play Syndrome)
Calling when you're convinced you're beat but the pot's big enough to compensate for the small chance you're wrong.
Anybody have any other's to add?