convolution

Concise Oxford English Dictionary © 2008 Oxford University Press:
convolution/kɒnvəˈluːʃn/

▶noun

• 1 a coil or twist.

  ■ a sinuous fold in the surface of the brain.

  ■ the state of being or process of becoming coiled or twisted.

• 2 a complex thing.

– derivatives
convolutional adjective.

– origin C16: from med. L. convolutio(n-), from convolvere (see convolve).