What is a Meta algorithm? I am currently reading a survey paper on the multiplicative weight update meta-algorithm. I am not quite sure what they mean by "meta-algorithm". Is it simply a general algorithm that can be used for different purposes? 

I couldn't find any exact definition for this term, though I have found examples of meta-algorithms such as Boosting in machine learning.
I interpret it as meaning "algorithmic technique".  It's a general framework that can be used to solve a number of problems.

Don't worry too much about the meaning of that phrase.  It's not something with an accepted definition, and you don't need to understand it to gain the value from that survey paper; it's just a passing phrase.  Instead, focus on understanding the ideas and technical results in the survey paper.