El Cajon (ĕl kähōnˈ) [key], city (1990 pop. 88,693), San Diego co., S Calif.; inc. 1912. Electronic equipment, aircraft parts, irrigation equipment, furniture, and men's suits are among its manufactures. El Cajon is a rapidly growing city; its population increased by nearly 70% between 1970 and 1990. Grossmont College is there.