This is a
Japanese term from the game of
Go (
Wei Qi/
Badouk). It is a compound term, coming from the individual terms "
keima" and "
shimari." For a more detailed explanation of these terms, see the relevant nodes, but basically, a
keima is an arrangement of stones that resembles the move of a
knight in
chess, and a
shimari is a
corner enclosure resulting from the same player playing two stones in the same corner.
The keima shimari is probably the most common form of shimari, and is shown below:
F......
E......
D..o,..
C....o.
B......
A......
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("," is the corner hoshi (star point) and is only for reference. It has no game effect, and can be ignored if you don't know what it is.)
The shimari is formed by stones on the 4-3 and 3-5 points, so is sometimes alternately called a 4335 enclosure. The two stones form a keima with one another and lay fairly secure claim to the corner territory, and radiate a reasonable amount of influence, especially in the upward direction. A stone in the vicinity of the left side hoshi (10-4 point) is now ideal for the person with the shimari (assuming the shimari is in the bottom left and facing as shown), especially if the facing corner is also owned by the same player, so the opponent will often play a wedge around 10-4 first, in order to prevent this.
A common fuseki for Black is what is known, on Sensei's Library, as the "Orthodox Fuseki." It is made by playing his first stone on a corner hoshi (the 4-4 point in one corner), then the next two so as to form a keima shimari in an adjacent corner, with the long side facing towards his hoshi stone, in order to threaten a play at 10-4 as I described.