A Darwin machine (a 1987 coinage by William H. Calvin, by analogy to a Turing machine) is a machine that, like a Turing machine, involves an iteration process that yields a high-quality result, but, whereas a Turing machine uses logic, the Darwin machine uses rounds of variation, selection, and inheritance.
In its original connotation, a Darwin machine is any process that bootstraps quality by using all of the six essential features of a Darwinian process: A pattern is copied with variations, where populations of one variant pattern compete with another population, their relative success biased by a multifaceted environment (natural selection) so that winners predominate in producing the further variants of the next generation (Darwin's inheritance principle).
More loosely, a Darwin machine is a process that uses some subset of the Darwinian essentials, typically natural selection to create a non-reproducing pattern, as in neural Darwinism. Many aspects of neural development use overgrowth followed by pruning to a pattern, but the resulting pattern does not itself create further copies.
Darwin machine has been used multiple times to name computer programs after Charles Darwin.