An element of meter in poetry. In quantitative verse, such as Greek or Latin, a dactyl is a long syllable followed by two short syllables. In accentual verse, such as English, it is a stressed syllable followed by two unstressed syllables.
[n] a finger or toe in human beings or corresponding part in other vertebrates
[n] a metrical unit with stressed-unstressed-unstressed syllables
An example of dactylic meter is the first line of Henry Wadsworth Longfellow's poem Evangeline, which is in dactylic hexameter:
This is the / forest prim- / eval. The / murmuring / pines and the / hemlocks,