urchin

noun

1. 1.A mischievous child.
2. 2.A street urchin, a child who lives, or spends most of their time, in the streets.
3. 3.A sea urchin.
4. 4.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.
5. 5.A neutron-generating device that triggered the nuclear detonation of the earliest plutonium atomic bombs.