Term: Blank Verse
Blank verse is a form based on unrhymed lines of iambic pentameter. The verse parts of Shakespeare's plays are blank verse (with exceptions, such as the witches' recipe), as is Milton's Paradise Lost. The form is one that is close to normal speech (indeed, "the form is one that's close to normal speech" is itself an iambic pentameter) so it gives a subtle pulse to a poem, rather than an obvious shaping as a limerick might. However, there is a tendency in contemporary poetry to use shorter lines, so the form can also sound stately or slow to a modern ear.
'The Waste Land' uses this effect, so that the difference between the lines "I read, much of the night, and go south in winter" and "What are the roots that clutch, what branches grow / Out of this stony rubbish?" are very much audible, the strict blank verse of the second section sounding instantly more oratorical than the looser metre of the earlier, more human, line. On the other hand, David Gascoyne's 'Prelude to a New Fin-de-Siecle' begins in blank verse and, as the poem turns to what exceeds the powers of poetry, the line length exceeds blank verse, stretching to hexameter, or even heptameter.
It is interesting to wonder if important pieces of blank verse such as in Shakespeare's plays, Paradise Lost and The Prelude are in blank verse because it sounds natural, or if they influenced speech so much that they made blank verse sound natural.