Definition of "digestion"

In the dead state all is apparently without motion. No agent within indicates design, intelligence, or foresight: there is no respiration; no digestion, circulation, or nutrition; […]

1822, John Barclay, chapter I, in An Inquiry Into the Opinions, Ancient and Modern, Concerning Life and Organization‎, Edinburgh, London: Bell & Bradfute; Waugh & Innes; G. & W. B. Whittaker, section I, page 2

As for Grierson, he poured liquor into himself as if it were so much soothing syrup, demonstrating that a good digestion is the highest form of good conscience.

1938, Norman Lindsay, Age of Consent, 1st Australian edition, Sydney, N.S.W.: Ure Smith, published 1962, page 159

Mostly, the microbiome is beneficial. It helps with digestion and enables people to extract a lot more calories from their food than would otherwise be possible. Research over the past few years, however, has implicated it in diseases from atherosclerosis to asthma to autism.

2013 June 29, “A punch in the gut”, in The Economist, volume 407, number 8842, pages 72–3