1. a small freshwater fish of the killifish family, often kept in aquariums
Usage: informal

Examples

• The pet store had several colorful killies in their tropical fish section.
• He bred killies in his home aquarium as a hobby.
• The killie darted between the aquatic plants in the tank.
• Many aquarists prefer killies because they’re hardy and easy to care for.
• The bright blue killie was the most popular fish at the aquarium show.