Definition
Someone who is excessively upbeat, encouraging and optimistic, often to the point where it may seem overly cheerful or naive.
Opposite In Meaning
How People Actually Use It
Polly Positive is the exact opposite of Negative Nancy. Polly Positive can describe someone who sees everything around them as absolutely fantastic. Polly Positive also describes someone in the case that their response to a specific event or state of being during a period of time is incredibly hopeful in its take on a situation.
"Person 1 (acting like a Negative Nancy): Man, I did not have fun at your friend's house: the music was too loud, it was too crowded, the people were annoying, everyone wrecked the place, the bathroom smelt awful, and now I am hungry. Person 2(acting like a Polly Positive): It is unfortunate that you did not have a good time, but I had a great time and thought everything was marvelous even including the smell."
Source: Urban Dictionary