Dactylic tetrameter is a metre in poetry.
[1] It refers to a line consisting of four dactylic feet.
"Tetrameter" simply means four poetic feet.
Each foot has a stressed syllable followed by two unstressed syllables, the opposite of an anapest, sometimes called antidactylus to reflect this fact.
A dactylic foot is one stressed syllable followed by two unstressed ones: A dactylic tetrameter would therefore be: Scanning this using an "x" to represent an unstressed syllable and a "/" to represent a stressed syllable would make a dactylic tetrameter like the following: The following lines from The Beatles' "Lucy in the Sky with Diamonds" demonstrate this, the scansion being: Another example, from Browning: Another example from Leonard Cohen of his song "Famous Blue Raincoat":