(Britain, obsolescent) A child who lives, or spends most of his or her time, in the streets; sometimes a petty thief or pickpocket.

(chemistry) A dense cluster of nanotubes having a form resembling a sea urchin, especially one made from vanadium oxides.

Any echinoderm of the class Spatangoida.

A porcupine fish.

plural of urchin fish

Any of numerous clypeastroid sea urchins (sand dollars) of the genera Melitta, Rotula and Encope, with one or more perforations resembling keyholes.

Any sea urchin of the genus Rotula having a round, flat shell; a type of sand dollar.

Any of the genus Clypeaster of echinoderms. See Clypeaster