Definition of a Verse

A verse can be defined as,

"A single metrical line in a poetic composition".

or

"A division of a metrical composition, such as a stanza of a poem or hymn".

or

"A succession of metrical feet written, printed, or orally composed as one line; one of the lines of a poem".
Verse in a Stanza
The term "verse" stands for any unit or group of words in such a composition, which traditionally had been referred to as a stanza. A verse can also be better understood as a constituent part of a stanza.

Origin and Epistemology

Before 900; Middle English vers ( e ), fers line of poetry, section of a psalm, Old English fers  < Latin versus a row, line (of poetry), literally, a turning, equivalent to vert ( ere ) to turn (past participle versus ) + -tus suffix of v. action.

Types of Verses

Blank Verse
It is poetry written in unrhymed iambic pentameter. It has been noted to be the most common and influential form of English poetry as most of the poems are written in blank verse form.
Free Verse
Free verse poems have no set meter, which is the rhythm of the words, no rhyming scheme, or any particularly defined structure. Some poets would find this liberating, being able to whimsically change your mind, while others feel like they could not do a good job in that manner.
Rhyming Verse
Rhyming verses consist of any poems with any number of verses set to rhyme with each other according to a set meter. Couplets, tercet and quatrian are common forms of poetry, consisting of rhyming verses.

A couplet essentially consist of two rhyming verses while in case of tercet and quatrain the rhyming is commonly found but not exactly mandatory.

Example of Verses

Blank Verse Example

Tomorrow, and tomorrow, and tomorrow,
Creeps in this petty pace from day to day,
To the last syllable of recorded time;
And all our yesterdays have lighted fools
The way to dusty death. Out, out, brief candle!
Life's but a walking shadow, a poor player
That struts and frets his hour upon the stage
And then is heard no more: it is a tale
Told by an idiot, full of sound and fury,
Signifying nothing.
-Excerpt from Macbeth

Free Verse Example

The fog comes
on little cat feet.
It sits looking
over harbor and city
on silent haunches
and then moves on.
-Carl Sandburg

Rhyming Verse Example

I felt a cleavage in my mind
As if my brain had split;
I tried to match it, seam by seam,
But could not make them fit.
The thought behind I strove to join
Unto the thought before,
But sequence raveled out of reach
Like balls upon a floor.
- Emily Dickinson