Definition of fish louse in English:

fish louse

noun

  • An aquatic crustacean which is a parasite of fish, typically attached to the skin or gills.

    an elongated crustacean that becomes permanently attached to the host and typically highly modified (class "Copepoda": several orders and numerous species).

    a free-swimming crustacean with a shield-like carapace and a pair of suckers (class "Branchiura": several genera, in particular "Argulus").