The term "decadent" is often used to describe food that is over-indulgent and rich in flavor; it is usually associated with food that is high in calories and therefore a "guilty pleasure."
The phrase "decadent food" is meant in a tongue-and-cheek way because the noun "decadent" actually denotes something that is "decaying or in decline." The term relates to the idea that certain food types are so indulgent that they must be bad for you.
Foods that may be described as "decadent" include: chocolate, caviar, wine, champagne, lobster, canapes and foi gras. Any type of food that is high in calories and rich in taste can be described as decadent.
The phrase "decadent food" is thought to have been coined from a verse in the Bible which states that overindulgence is sinful and may lead to ruin. However, the phrase in contemporary society no longer has a religious context.