I often hear the word gold as a slang to describe something great such as "last night's party was gold" or "that movie was gold" etc. What exactly does gold mean and how do you use the slang?
It is commonly referred to as merit and stems from the rarity of gold and its use in medallions such as "Gold Medals." (Even this very Q&A board uses Gold / Silver / Bronze in its token system)
It is closest described as "priceless" when used in the context you described.