“It's such a waste of time.”

You're talking to a friend about Facebook. You are trying not to use it. You want to explain why to your friend. You say:

It's such a waste of time.

such a (something)

The word "such" is similar to "so" except it's used with nouns instead of adjectives:

He's so handsome.

He's such a good-looking man.

a waste of time

When something is "a waste of time", it means that you spend a lot of time doing it, but don't get any benefits from it in the end. This is a common phrase people use when they're talking about things that:

• they have to do but don't want to do (like waiting in a line)
• they want to do but don't think are useful (like playing video games or using some websites)