- 1[intransitive, transitive] (of relationships, attitudes, people, etc.) to change so that they become less pleasant or friendly than before; to make something do this The atmosphere at the house soured. sour something The disagreement over trade tariffs has soured relations between the two countries.
- 2[intransitive, transitive] sour (something) if milk sours or if something sours it, it becomes sour and has an unpleasant taste or smell
NAmE//ˈsaʊər//Verb Forms present simple I / you / we / they sour
he / she / it sours
past simple soured
-ing form souring