In contract bridge, an overcall is a bid made after an opening bid has been made by an opponent; the term refers only to the first such bid. A direct overcall is such a bid made by the player seated immediately to the left of the opener, i.e. next in the bidding rotation; an overcall in the 'last seat', i.e. by the player to the right of opener, which is made after two intervening passes, is referred to as a balancing overcall.
The overcaller has one or more of the following objectives:
In most bidding systems, an overcall in an unbid suit is natural denoting length and strength in the suit bid. The common requirements include:
The rule of thumb is that the weaker a hand is in high card points, the better the bid suit should be (i.e., longer or with stronger honors).
According to modern bridge theory, the following hands warrant a 1♥ overcall over an opposing 1♣ or 1♦ opening:
♠ 632 ♥ AKJ96 ♦ 8752 ♣ 4
♠ A32 ♥ AKJ96 ♦ 752 ♣ 104
♠ A3 ♥ AK986 ♦ KQ5 ♣ 742
Stronger hands such as ♠ A3 ♥ AK986 ♦ KQ5 ♣ Q42 are considered too strong for an overcall, and should be bid via a takeout double followed by the most economical rebid in hearts.
Notrump overcalls at the one-level normally indicate 15-18 HCP in a balanced hand, with at least one stopper in opponent's suit. Usually, Stayman is on but transfers are off.
The hand ♠ KJ63 ♥ AQ2 ♦ A84 ♣ Q93 is suitable for a 1NT overcall over any opening bid, as well as a 2NT overcall over an opponent's weak two bid.
Jump overcalls are made by skipping one level of bidding, e.g. 1♦ - (2♠).
Jump overcalls are classified according to strength of hand as weak, intermediate, and strong. In the United States weak jump overcalls are currently considered normal, while intermediate and strong overcalls are not expected by the opponents and those treatments of the bid by partnership agreement require that the opponents be alerted to the meaning of the bid.
The Four Aces team (David Burnstine and others) introduced the weak, "preemptive jump overcall" in the U.S. late in 1933, but the strong treatment was standard for decades, following the popular authorities Ely Culbertson and Charles Goren whose bidding systems incorporated the strong. Goren adopted the weak treatment in May 1955, two months before the ACBL introduced its first convention card, with "Pre-emptive single jump overcalls and responses" one of ten pre-printed items to be marked if applicable.
According to The Official Encyclopedia of Bridge, published by ACBL, the definitions of the three bids are as follows:
Thus, a weak jump overcall of 2♠ would be made with ♠ KQJ653 ♥ J53 ♦ 432 ♣ 3, while an intermediate jump overcall of 2♠ would be closer to or including opening bid values, like ♠ QJT532 ♥ AK3 ♦ J43 ♣ 3 or ♠ AKJ432 ♥ 3 ♦ 43 ♣ K432.
Strong jump overcalls are not commonly used in today's game except over a weak preemptive bid by an opponents. After 2♦(weak), a jump overcall of 3♠ would reflect a hand such as ♠ AKQ543 ♥ AQ3 ♦ K94 ♣ 5.
Some partnerships utilise more exotic overcalls. An example are the canapé overcalls used by the Italian top pair Norberto Bocchi and Giorgio Duboin. In canapé overcalls the suit bid typically contains a three card, whilst the hand contains a five card in another suit.
The partner of the overcaller is called the Advancer. In response to partner's overcall, Advancer typically bids as follows: (Players may agree to slightly different methods)