ELF, a diminutive supernatural being of Teutonic mythology, usually mischievous, causing diseases and evil dreams, stealing children and substituting changelings ; differs from the Romanic, less sinister fairy. (O.E. ael f ; cf. Ger. Alp, nightmare.) The prehistoric flint implements, in England known as "elf-bolts" or "elf-arrows," were looked on as the weapons of the elves, with which they injured cattle. A tangle in the hair was called an "elf-lock."