Unrhymed verse.
Iambic pentameter couplets are often called Heroic couplets. Unrimed Iambic Pentameter is called Blank Verse. But I do not know of a generic alternate term for Iambic Pentameter.
Blank verse is poetry with a regular meter but no rhyme. Unrhymed iambic pentameter is a specific type of blank verse. "Pentameter" means each line of poetry has 5 feet. In poetry, a "foot" is a small group of syllables. In English, "iambic" means each foot has two syllables, an unstressed syllable followed by a stressed syllable (different for Latin and other languages).
Blank verse does not have rhymes.
Blank Verse
Blank verse is poetry written in un rhymed iambic pentameter.
Shakespeare wrote a lot of dialogue in his plays in blank verse, which is unrhymed iambic pentameter.
Rhyme does not appear in blank verse. Blank verse is a form of poetry that does not have a rhyme scheme, but has a consistent meter, often iambic pentameter.
In Julius Caesar, Antony speaks in blank verse.
A verse.
Shakespeare's blank verse was composed in blank verse, which is to say unrhymed iambic pentameter. Unless you want to know where he did his writing to which question nobody knows the answer.
Free verse has variable rhythm.
A verse with no rhyme but with meter is called blank verse. Blank verse is a form of poetry characterized by a consistent meter, most commonly iambic pentameter, but lacking a rhyme scheme. It is often used in dramatic works and epic poetry.