Definition of miller's thumb in English:

miller's thumb

noun

  • A small European freshwater fish of the sculpin family, having a broad flattened head and most active at night.

    Also called bullhead
    • ‘Lampreys and miller's thumbs may not be caught but poisoning by liquid manure or destruction of their environment by modern land drainage schemes goes unpunished.’
    • ‘Also in the river are miller's thumbs and lamprey, a prehistoric fish, that buries into silt when young and behaves like a worm.’
    • ‘They are also called miller's thumbs in some parts of the country.’
    • ‘There's also the problem that in streams with lots of miller's thumbs, rocks to hide under are the limiting factor.’