virus that destroys bacteria, 1917, an abbreviated form of bacteriophage.
word-forming element meaning "eater," from stem of Greek phagein "to eat" (see -phagous).
phage (fāj)n. See bacteriophage.
-phage suff. One that eats: macrophage.
A program that modifies other programs or databases in unauthorised ways; especially one that propagates a virus or Trojan horse. See also worm, mockingbird. The analogy, of course, is with phage viruses in biology. [Jargon File]