A blast in a coal mine which--due to improperly placed charges, the wrong kind
or quantity of explosives, or insufficient stemming--expends most of its force
on the mine air; it sometimes ignites a gas mixture, coal dust, or both, thus
causing a secondary explosion, which may or may not spread throughout the mine;
a shot that blows out without disturbing the coal; a shot that is not properly
directed or loaded; a blown-out shot. Fay
Source:
Dictionary of Mining, Mineral, and Related Terms
