An adaptive test is a test in which the quality of answers to early questions determine the difficulty of questions selected later in the test. It is typical of language test that cover large differences in language proficiency. High-proficiency takers don't want to spend time answering what they find to be overly simple questions, whilst low-proficiency takers don't want to spend time answering questions that are obviously too difficult. The early questions can determine coarse levels, and the finer grading can be narrowed down by later questions.
This is often a feature of computer-based testing, but it's also possible to conduct an oral interview test in a similar way. Paper-based testing in this manner would probably reduce test practicability below acceptable levels, and is not commonly practised.