General:
* A single example or representative of a group or class: For example, "a specimen of fine handwriting."
* A sample of something, especially for examination or analysis: For instance, "a blood specimen."
Scientific/Biological:
* An organism, part of an organism, or substance used for study or examination: This is the most common meaning in science and medicine. Examples include a plant specimen, a tissue specimen, or a specimen of a rare insect.
Other:
* A copy or reproduction, especially a model: For example, "a specimen of a Roman coin."
* Something of outstanding quality or merit: This meaning is less common and often used figuratively.
The meaning of "specimen" is usually clear from the context.