Definition of "as if" in English

Conjunction

1. As though; in a manner suggesting.

   • The old man stumbled, as if he were about to fall.
   • It looks as if it's going to rain.
   • She jumped all of a sudden, as if stung.

2. In mimicry of.

   • When the teacher’s back was turned, the class clown would hold his stomach as if he were ill.

3. Indicating something that the speaker deems very unlikely, or is adamant that he or she would not do (see also interjection sense below).

   • How can you even think that? As if I would inform on you to the police!

Interjection

1. Indicates that the speaker deems something highly unlikely.

   • "I'm going to clean your whole house." — "As if!"
   • Me, take up yoga and become a vegetarian? As if!