To shut in or to seal in or to fence in or to hem in or to enclose or to surround or to blockade a group of stones: these are flavours of a core aspect of Go, the surrounding game. Mostly, shut in, seal in, fence in and enclose refer to a group which is half surrounded by the opponent, half facing corner or side, moreover in a severe way, whereas surrounded is more general.
allows to seal White's group into the top left corner.
Bob McGuigan: is a clever move that is far from obvious since leads to the capture of . But these three black stones are now short of liberties and Black can no longer play at a as a local ko threat. If he does then White plays atari at b and captures the two black stones at and a or the three black stones including by playing atari at c.