- 1[intransitive, transitive] fog (something) (up) if a glass surface fogs or is fogged up, it becomes covered in steam or small drops of water so that you cannot see through
- 2 [transitive] fog something to make someone or something confused or less clear I tried to clear the confusion that was fogging my brain. The mayor was trying to fog the real issues before the election.
NAmE//fɔɡ//, NAmE//fɑɡ//Verb Forms present simple I / you / we / they fog
,he / she / it fogs
,past simple fogged
,-ing form fogging