flake

(noun) a person that you can’t rely on because they are not dependable

Example Sentences:

The students thought their new professor was a flake because he always started class 10 minutes late and ended class 10 minutes early.

A: Are you having fun with your new boyfriend?
B: Sometimes. He’s kind of a flake. He always cancels our plans at the last minute.

My mom asked Hailey to pick her up from the airport, because she said I would probably be late because I’m such a flake.

From the Blogs:

Anti-War Obamabots Flakey Position

Media:

Similar idioms:

1. flakey
2. clamp down on something
3. have a bone to pick with someone
4. better late than never
5. epic fail