In the game of
Go (
Wei Qi/
Badouk), a pincer is one possible response to a
kakari (
corner approach), the other two being to defend, or
tenuki (ignore the
kakari and play elsewhere). In a pincer, the player responds to the
kakari by playing on the far side of the
kakari stone, rather than immediately defending his corner. Consider the following White
kakari "o" to Black's
hoshi stone "x" (played some time earlier)(edge of the
goban marked with ###):
#######
#......
#......
#......
#...x..
#......
#..o...
#......
#..ab..
#..cd..
#..ef..
#......
A Black move at any of a, b, c, d, e or f would be a pincer. The nomenclature for talking about pincers is to specify the number of empty points separating the pincer from the kakari, and "low" for the 3rd line, or "high" for the 4th line. So "d," for instance, would be a "two-space high pincer." To be more specific, you could also specify the location of the corner stone and the type of kakari, e.g. "two-space high pincer to a keima kakari on the hoshi stone."
A pincer is an aggressive move. It attacks the opponent's kakari stone strongly by denying it a base (secure eye space), but leaves the corner and the pincer stone itself somewhat weak if there are no friendly stones about. Thus, it will often lead to some sort of fight, which can get complicated. If the opponent has a strong group nearby, the fight will favor him, so a pincer is not recommended. If you have a strong group nearby, the fight will favor you, and you should usually pincer. If neither player has any stones nearby, to pincer or defend the corner is mostly a matter of taste.
Common responses to a pincer include jumping towards the center with ikken tobi (a in the diagram below), diving into the corner by invading the 3-3 point (b in the diagram below. Note: not an option if you're talking about a kakari to a 3-4 point, instead of 4-4), a slide (c in the diagram below. Usually not recommended in the case of a 4-4 corner stone as shown here, but common when that stone is at 3-4 instead), a contact play to either the corner stone or the pincer stone (the two ds in the diagram), a counter-pincer if you're very confident in your fighting skills (e in the diagram below), or some kind of clever play intended to sacrifice the original kakari stone to build thickness along the upper side, maybe starting somewhere like f (though this is just a guess... if someone knows a good way to set up a sacrifice, let me know).
#######
#......
#......
#..b...
#.cdx..
#....f.
#..o.a.
#......
#..xd..
#......
#..e...
#......
Pincer joseki are often quite complicated, and players at my kyu level (around 10 or 12k) often don't really know very many. Most of the players I play on IGS are quite fond of fighting, however, and tend to pincer almost any kakari I play, much to my chagrin.