What is the term for a metaphor that is developed over an extended passage?

The term "Extended Metaphor" refers to a metaphor that is elaborated upon throughout a significant portion of a text, allowing for a deeper exploration of the ideas or themes being illustrated. This literary device can enhance the reader's understanding by providing multiple layers of meaning and making comparisons that resonate more profoundly within the context of the passage. For example, a writer might introduce a metaphor at the beginning of a poem and continue to develop it in various ways, using imagery and language that relate back to the initial comparison, which enriches the text.

In contrast, onomatopoeia refers to words that imitate sounds, such as "buzz" or "clang," and does not pertain to extended comparisons. Parallel construction involves the use of similar grammatical structures in a sequence of words or phrases, which is distinct from metaphorical elaboration. A noun is simply a part of speech that denotes a person, place, thing, or idea and does not relate to the concept of metaphorical development at all. Therefore, "Extended Metaphor" is indeed the most fitting term for a metaphor that is fully developed over a passage.