as if

1) in such a way that something seems to be true

It looks as if it's going to rain.

Jack smiled as though he was enjoying a private joke.

2) used when you are describing something and you imagine an explanation for it that you know is not the real one

The house was in such a mess – it looked as though a bomb had dropped on it.

3) spoken used for emphasizing that something is not true or is not important

"Don't get lost or anything, will you?" "As if I would – I'm not stupid."

Why was he worrying about the interview? – As if it mattered anyway!