What is junk food?

According to Merriam-Webster - “1. Food that is high in calories but low in nutritional content. 2. something that is appealing or enjoyable but of little or no real value.”

According to https://www.definitions.net/definition/junk+food “Junk food is a derisive slang term for food that is of little nutritional value and often high in fat, sugar, salt, and calories. ... Despite being labeled as "junk" consuming such foods usually does not pose any immediate health concerns and is generally safe when integrated into a well balanced diet.”