Webster's Revised Unabridged Dictionary · 1913

Sour

Sour , adjective

[Old English sour, sur, Anglo-Saxon s{not transcribed}r; akin to Dutch zuur, German sauer, Old High German s{not transcribed}r, Icelandic s{not transcribed}rr, Swedish sur, Danish suur, Lithuanian suras salt, Russ. surovui harsh, rough. Compare Sorrel, the plant.]

1.
Having an acid or sharp, biting taste, like vinegar, and the juices of most unripe fruits; acid; tart.
All sour things, as vinegar, provoke appetite. — Bacon
2.
Changed, as by keeping, so as to be acid, rancid, or musty, turned.
3.
Disagreeable; unpleasant; hence; cross; crabbed; peevish; morose; as, a man of a sour temper; a sour reply.
A sour countenance. — Swift
He was a scholar... Lofty and sour to them that loved him not, But to those men that sought him sweet as summer. — Shakespeare
4.
Afflictive; painful.
Sour adversity. — Shakespeare
5.
Cold and unproductive; as, sour land; a sour marsh.
Collocations (5)
Sour dock (Botany) , sorrel.
Sour gourd (Botany) , the gourdlike fruit Adansonia Gregorii, and Adansonia digitata; also, either of the trees bearing this fruit. See Adansonia.
Sour grapes , See under Grape.
Sour gum (Botany) , See Turelo.
Sour plum (Botany) , the edible acid fruit of an Australian tree (Owenia venosa); also, the tree itself, which furnished a hard reddish wood used by wheelwrights.

Sour , noun

A sour or acid substance; whatever produces a painful effect. — Spenser

Sour , transitive verb

[Anglo-Saxon s{not transcribed}rian to sour, to become sour.]

1.
To cause to become sour; to cause to turn from sweet to sour; as, exposure to the air sours many substances.
So the sun's heat, with different powers, Ripens the grape, the liquor sours. — Swift
2.
To make cold and unproductive, as soil. — Mortimer
3.
To make unhappy, uneasy, or less agreeable.
To sour your happiness I must report, The queen is dead. — Shakespeare
4.
To cause or permit to become harsh or unkindly.
Souring his cheeks. — Shakespeare
Pride had not sour'd nor wrath debased my heart. — Harte
5.
To macerate, and render fit for plaster or mortar; as, to sour lime for business purposes.

Sour , intransitive verb

To become sour; to turn from sweet to sour; as, milk soon sours in hot weather; a kind temper sometimes sours in adversity.
They keep out melancholy from the virtuous, and hinder the hatred of vice from souring into severity. — Addison