Definition of blue pigeon in English:

blue pigeon

Pronunciation /ˌbluː ˈpɪdʒ(ɪ)n/

noun

  • 1Any of various chiefly tropical pigeons having bluish plumage; (now) especially pigeons of the genus Alectroenas, found on islands in the western Indian Ocean.

  • 2Nautical
    slang The lead attached to the sounding line; the plummet. Now chiefly historical.

Origin

Late 17th century (in an earlier sense). From blue + pigeon.