Saint Elmo's fire Meaning, Definition & Usage

  1. noun an electrical discharge accompanied by ionization of surrounding atmosphere
    Saint Ulmo's light; Saint Elmo's light; St. Elmo's fire; Saint Ulmo's fire; corona discharge; corona; corposant; electric glow.

WordNet

Definitions
  1. a luminious, flamelike appearance, sometimes seen in dark, tempestuous nights, at some prominent point on a ship, particularly at the masthead and the yardams. It has also been observed on land, and is due to the discharge of electricity from elevated or pointed objects. A single flame is called a Helena, or a Corposant; a double, or twin, flame is called a Castor and Pollux, or a double Corposant. It takes its name from St. Elmo, the patron saint of sailors.

Webster 1913