You can't build up a vocabulary if you never meet any new words. And to meet them you must read. The more you read the better. -- Rudolf Flesch and Abraham Lass
I am a fan of the useful words for different occasions. In fact, finding a new word from time to time is the bonus of writing a blog.
Pollyanna is the newest word I picked up recently. And it refers to a person who is blindly optimistic and is therefore incapable of any reality-based problem-solving. Think of being unrealistically pollyannaish about sales numbers. :)
It can also be used to describe people who make light of a serious situation. For example, a person who advises a woman to stay in a violently abusive marriage.
The word is used majorly in a negative sense. Use the word for someone who refuses to see the truth in a difficult situation and continues to be hyper optimistic.
The word has its derivation from the novel Pollyanna (1913) by the American fiction writer Eleanor Porter, where Pollyanna is the very name of the novel's female protagonist.