What is the definition of Upgrade in the stock market?

An upgrade is a term used for a company or investment security that has a positive expectation.  For example, when an analyst upgrades a stock, the stock price usually goes up because that good news for the company.  However, the stock price increase is not always the case.

The stock of a company could be upgraded when the future is promising and it could also be downgraded when things are expected to go opposite for the underlying company.  A stock downgrade is the opposite of an upgrade.