any part of an organism such as an organ or extremity

one of the bony outgrowths on the heads of certain ungulates

any hard protuberance from the head of an organism that is similar to or suggestive of a horn

a showy growth of e.g. feathers or skin on the head of a bird or other animal

temporary outgrowth used by some microorganisms as an organ of feeding or locomotion

a lash-like appendage used for locomotion (e.g., in sperm cells and some bacteria and protozoa)