as if

1. Like. I have such a terrible headache—I feel as if my head is going to explode. I did tell her that I wouldn't be home for dinner tonight. It's as if she doesn't listen to me at all! After traveling all night, I felt as if I could fall asleep standing up.

2. An interjection indicating complete dismissal of what has been said or suggested, implying that it is not the case or would never happen. A: "Tim thinks he's going to go to the prom with you." B: "As if! I'd rather go by myself." Please, like Alice would ever take the trash out—as if! As if! There's no way I'm staying home on a Saturday night!

as though

Similar to, likened to, or fashioned after something like it were the truth. So many bad things happened all at once, it's as though life itself were against me. He acts as though he's some famous author, though really he's only ever published a single short story. Anyone who talks as though they know more than anyone else is a fool, plain and simple.

as if

Also, as though. As it would be, as in He decided to accept, as if it really mattered, or John scowled as though he were really angry. The first idiom dates from the late 1500s, the variant from the late 1700s. Also see make as if.

as ˈif

(spoken) used to express anger at or disapproval of a suggestion, an explanation, etc., or to deny a possibility: As if I really cared! ♢ ‘Don’t tell Tom I said that, will you?’ ‘Oh, as if (I would)!’

as if/as though

in a way that suggests something: He behaved as if nothing had happened. ♢ It sounds as though you had a good time.