Originally: belonging to the group Malacopterygii, comprising bony fishes having fins supported by soft (i.e. segmented and often branched) rays. Later: designating or relating to fishes having such fins.
A malacopterygian fish.
Mid 19th century; earliest use found in William Kirby (1759–1850), entomologist and naturalist. Probably from French malacoptérygien from malaco- + -ptérygien, after scientific Latin Malacopterygii.