Free verse refers to poetic verse that does not adhere to formal structures. As such, free verse lacks a regular meter or rhyme scheme. 

Verse evolved from the Old English word fers, from the Latin versus (“line, line of writing”). Free evolved from the Old English word freo, which has the same meaning as the modern term.

An example of a free verse poem is Mary Oliver’s “Banyan”:

Something screamed
from the fringes of the swamp.
It was Banyan,
the old merchant.
It was the hundred-legged
tree, walking again.
The cattle egret
moved out into the sunlight,
like so many pieces of white ribbon.
The watersnakes slipped down the banks
like green hooks and floated away.

see: verse, poetry, rhyme