Having a tart or acid taste, such as that which is characteristic of unripe fruits and vinegar. Also said of taste. (Opposed to sweet, and…

Somewhat sour, in various senses. Of things, taste, or smell.

Resembling or (in early use) containing vinegar; sour or acidic like vinegar. Also figurative or in figurative context.

Having a marked effect on the taste or other senses. Esp. of wine or beer: sour, acid, tart. In later use English regional (northern and Dorset) and…

Of or relating to vinegar; producing or containing vinegar or (esp. in later use) acetic acid; of the nature of or resembling vinegar; sour. Also…

Of the nature of the crab-tree or its fruit; figurative sour-tempered, peevish, morose; harsh.

Somewhat sharp.

(un-, prefix1 affix 2.)

Of milk: ? Skimmed (in quot. 1594 apparently stale, sour; perhaps associated with flat, adj.).

Of the town of Ameria, in Umbria, Italy.

= acetose, adj.

Of food or flavour: astringently sour or harsh-tasting.

In general use: sour, tart, sharp to the taste; tasting like vinegar.

Slightly acidic; sharp-tasting, sour.

‘Having a taste compounded of saltness and sourness’ (Johnson).

Tending to turn acid or sour; acidic; sour. Also figurative. Now chiefly historical.

Without sugar, unsugared.

= acidulous, adj. 1 2. Now rare.

Of milk, etc.: Slightly sour. Cf. blink, v. 7.

Of wines: unsweetened.