Definition of "subacid"

Beer may be considered as the wine of grain, for it is the product of the fermentation of malt, just as wine is that of the fermentation of the grape, or other subacid fruits.

1821, Friedrich Accum, A Treatise on the Art of Brewing, London: Longman, Hurst, Rees, Orme, & Brown, page 5

An excellent temper, with a slight degree of subacid humour.

1827, [Walter Scott], Chronicles of the Canongate; […], volumes (please specify |volume=I or II), Edinburgh: […] [Ballantyne and Co.] for Cadell and Co.; London: Simpkin and Marshall

Summerlee drew him on with his chorus of subacid criticism, while Lord John and I laughed at the contest and the lady, her hand upon his sleeve, controlled the bellowings of the philosopher.

1913, Arthur Conan Doyle, “(please specify the page)”, in The Poison Belt […], London; New York, N.Y.: Hodder and Stoughton

Rosellas, a fruit, I imagine, not very well known, we grew most successfully, its delicious sub-acid making the most splendid substitute for the English red currant; and we varied its uses by transforming the raw material into jam and jelly, and freshly-stewed fruit.

1887, Harriet W. Daly, Digging, Squatting, and Pioneering Life in the Northern Territory of South Australia, page 122