Final answer:
An intermediate host is where a parasite develops but does not reach maturity, which is essential for the completion of the parasite's life cycle.
Step-by-step explanation:
A host in which a parasite undergoes development but does not reach maturity is called an intermediate host. In the complex life cycle of a parasite, the intermediate host is critical as it provides an environment for the parasite to go through specific stages of its life cycle before moving on to the final or definitive host, where it will reach maturity and potentially reproduce. Examples of this include tapeworms and flukes, with each requiring multiple different hosts to complete their lifecycle.