test subject; experimental subject
Used especially for animals or objects in experiments, rather than human participants. For human subjects, 被験者 (ひけんしゃ) is more common.
To confirm the safety of the new drug, mice were used as test subjects.
In this experiment, care was taken not to stress the test subjects.
Compound of 被 (ひ, 'receive') + 験 (けん, 'test') + 体 (たい, 'body'). The term is a modern technical coinage for experimental subjects, especially non-human ones.