jack a general name often used for species of fish in the extensive family Carangidae. These are surface swimmers, with a coloration designed to help them evade detection by predators: blue-green backs and silvery undersides. They almost all inhabit tropical or subtropical waters. Size varies considerably, but relatively narrow bodies are standard. See also horse mackerel; scad; trevally; pompano; amberjack.
The reason for the name is unclear, and it does not translate directly into other languages. The name jack is also applied in a more specific way to some of the carangid species, notably:
Caranx hippos, crevalle jack, a circumglobal tropical fish which has commercial importance in SE Asia. Maximum length: 1 m (40").
C. ignobilis, yellowfin jack, slightly larger, called maliputo by Filipinos, who esteem it greatly (especially those caught in the volcanic Lake Taal, whose flesh is said to be delicately flavoured by the sulphur in the lava rock).