What does this icon mean?

[Skyline15]

I have been getting this icon on my HTC one m8 for the past two days, anyone knows what it means? It looks like the no symbol.

 

[B. Diddy]

Welcome to Android Central! It means you're set to No Interruptions. Press the volume button, then tap All. See here for more info: Ask AC: What's that star in my notification area? | Android Central