/flash"ing/ , n.
1. Building Trades. pieces of sheet metal or the like used to cover and protect certain joints and angles, as where a roof comes in contact with a wall or chimney, esp. against leakage.
2. the act of creating an artificial flood in a conduit or stream, as in a sewer for cleansing it.
3. Photog. , Motion Pictures. the process of increasing film speed by exposing undeveloped film briefly to a weak light source before using it or of exposing photographic printing paper to reduce contrast.
[ 1775-85; FLASH + -ING 1 ]