Blank verse is one of the most common forms of English poetry and it has been estimated that about three-quarters of all English poetry is in blank verse. Tennyson's blank verse in poems like "Ulysses" and "The Princess" are good examples of this as well as "Tears, Idle Tears.”
Charlotte Mason had her students write more blank verse poetry than any other form of poetry. They were asked to scan various blank verse poems as well to determine the meter. EXAMPLE. Grammar of Poetry by Matt Whitling teaches my year 7 students how to do this. More help with this pdf HERE.
Blank verse is poetry written in regular metrical but unrhymed lines and is almost always iambic pentameters. When a pair of syllables is arranged as a short followed by a long, or an unstressed followed by a stressed, pattern, that foot is said to be "iambic". The English word "trapeze" is an example of an iambic pair of syllables, since the word is made up of two syllables ("tra—peze") and is pronounced with the stress on the second syllable ("tra—PEZE", rather than "TRA—peze")
So basically, blank verse is iambic pentameter without rhyme:
Da-DA, da-DA, da-DA, da-DA, da-DA
Please note the blank verse is distinctly different from free verse.
“Free verse is an open form of poetry. It does not use consistent meter patterns, rhyme, or any other musical pattern. It thus tends to follow the rhythm of natural speech.” (Wikipedia)