Sea-stack

The sea-gull sprang upwards from where he had floated on the ripple, and hied him slowly away to his lodge in his deep sea-stack; the dusky cormorant flitted past, with heavier and more frequent stroke, to his whitened shelf high on the precipice; [...]

Source: wiktionary

That this defile may have been partly eroded by the action of the sea is also very probable; and there are certain isolated pinnacles and irregular columns of agglomerate in its immediate neighbourhood which have all the appearance of being old sea-stacks.

Source: wiktionary

The sea, with its tremendous battering-power, is excavating caves, just as the streams make pot-holes; only the action is horizontal, rather than vertical, the water lashing like a whip around the flanks of the sea-stacks and islets.

Source: wiktionary