Mimetic things imitate or echo something else. A mimetic pattern on the wings of a bird might look just like the pattern on tree bark or the leaves of a plant.
You'll most often find the adjective mimetic in technical or scholarly writing, discussing mimetic designs and characteristics in nature. Or you might refer to mimetic techniques in art and writing. Sometimes literary realism in novels and poetry is described as mimetic, since it reflects or echoes what really happens in the world. Mimetic comes from the Greek root mimetikos, "good at imitating."