D defs.my
Entry 1 sense Webster, 1913

Serbonian

· Ser·bo·ni·an · IPA /sɚˈboʊ.ni.ən/
01 a. Relating to the lake of Serbonis in Egypt, which by reason of the sand blowing into it had a deceptive appearance of being solid land, but …
  1. 1.
    Relating to the lake of Serbonis in Egypt, which by reason of the sand blowing into it had a deceptive appearance of being solid land, but was a bog.
    “A gulf profound as that Serbonian bog . . . Where armies whole have sunk.” Milton.