Definition of rivulus in US English:

rivulus

noun

  • A small tropical American fish of shallow fresh and brackish water. Often mistaken for a killifish or topminnow, the rivulus is distinguished by its tubular nostrils.

    Genus Rivulus, family Rivulidae: several species, many of which are spotted, in particular R. marmoratus

Origin

Modern Latin, from Latin, literally ‘small stream’.

Pronunciation

rivulus

/ˈrivyələs/