Blank verse is unrhymed poetry with each line having the same meter - that is each line has the same number of syllables with those syllables creating a regular rhythm.   

Something there is that doesn't love a wall,
That sends the frozen-ground-swell under it,
And spills the upper boulders in the sun,
And makes gaps even two can pass abreast.
         First four lines of "Mending Wall" by Robert Frost