IDL is an acronym for:

• International Date Line
• Interface description language, the generic term for interface description languages
• IDL specification language, a specific interface description language
• Interactive data language, an statistical programming language
• Intermediate density lipoprotein

• New York International Airport (IATA) at Idlewild in New York, New York - When its name was changed to John F. Kennedy International Airport it got JFK as IATA code.