What is the meaning of Urchin?

A mischievous child.

A street urchin, a child who lives, or spends most of their time, in the streets.

A sea urchin.

One of a pair in a series of small card cylinders arranged around a carding drum; so called from its fancied resemblance to the hedgehog.

A neutron-generating device that triggered the nuclear detonation of the earliest plutonium atomic bombs.

A hedgehog.

A mischievous elf supposed sometimes to take the form of a hedgehog.

Source: wiktionary.org