With respect to stock recommendations, what does "Upgraded from Neutral to Overweight" mean?

Nuetral means - Hold, Dont sell or dont buy.

Over Weighted - It reached the expectations and the target, it may start decline from that point, overweight than the sensex growth.

It means that the one reviewing the stock now has a higher opinion that an opinion previously expressed .

It;s another way of saying the reviewer is gaining confidence about a particular recommendation previously made.

nuetral implies no opinion...overweight means to start adding to your position or start slowly with a new position.

But more often than not it means its time to start unloading since these analysts are often herd followers and they tend to say buy when you should be selling, and visa versa.