any of about 300 species of abundant deep-sea fishes of the family Macrouridae found along the ocean bottom in warm and temperate regions. The typical grenadier is a large-headed fish with a tapered body ending in a long, ratlike tail bordered above and below by the anal and second dorsal fins. The eyes are large, and the mouth is on the underside of the head. The often extended snout presumably aids in rooting about the bottom for food. Some species have light organs, and some can produce sounds by means of paired muscles attached to the swim bladder. The fish is usually about 30 to 60 cm (1 to 2 feet) long.

During the 18th century there was a gradual decline in the use of grenades, but grenadiers were retained as elite troops. The gradual adoption throughout Europe of the four-company battalion progressively encouraged the recruitment of separate grenadier formations, but their duties had come to differ little from those of the ordinary regiments of the line. Horse grenadiers made a brief appearance in the British and Belgian forces. In World War I, battalion subunits were trained both to throw hand grenades and to fire rifle grenades. The grenadier has since disappeared as a special type of infantryman, and the term has become obsolete save in historical names such as the Grenadier Guards.