English in a Minute: Sleep Like a Rock(ZT)
http://learningenglish.voanews.com/media/video/english-in-a-minute/2688206.html?z=0&zp=1
---I remember you said you were getting a new bed last weekend. How do you like it?
---I love it. My old bed totally bit the dust, but the new mattress is great. I slept like a rock last night.
---That is good to know. I have not been sleeping well at all lately. Maybe I should get a different mattress, too.
If you slept like a rock, you slept very well. You cannot wake a rock, because it is not alive. You can also say you slept like a log, to mean the same thing. And that's English in a minute.
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My old car finally bit the dust.
This pen is out of ink and has bitten the dust.
http://idioms.thefreedictionary.com/bite+the+dust