This refers to a channel, crevice or passage full of windings and turnings, not quite a maze, though some mazes certainly take on an anfractuous appearance, one that is sinuous or winding.
One sense is of a broken or jumbled landscape:
Paint me a cavernous waste shore
Cast in the unstilled Cyclades,
Paint me the bold anfractuous rocks
Faced by the snarled and yelping seas.
Sweeney Erect, by T S Eliot, 1919.
Anfractuosity and anfractuous are also used in the sense of the sulci, the grooves between the convolutions of the surface of the brain.
This is yet a third, figurative, sense:
If any message from the core of reality ever were to reach us, we should expect to find in it just that unexpectedness, that willful dramatic anfractuosity which we find in the Christian faith.
The Problem of Pain, by C S Lewis, 1940.
The term is used in modern times to refer to a kind of opaque and circuitous legal prose, full of twists and turns, seemingly designed more to confuse than to clarify; this is sometimes called syntactic anfractuosity, a suitably ponderous term with which to describe its subject.
The word comes from Latin anfractus, a bending around, from the verb frangere, to break. So it is a close cousin of the much more recent fractal, as well as fracture, fragile, refraction, and, rather less obviously, infringe and osprey (this last word comes from ossifraga, bone breaker, originally applied to the lammergeier).