urchin

noun7

1. •
   A mischievous child.
2. •
   A street urchin, a child who lives, or spends most of their time, in the streets.

   • And the urchins that stand with their thievish eyes / Forever on watch ran off each with a prize. — 1879
3. •
   A sea urchin.
4. •
   (historical) A neutron-generating device that triggered the nuclear detonation of the earliest plutonium atomic bombs.
5. •
   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.

   • Here we have a carding-engine, with the drum surmounted with urchin or squirrel cards[…] — 1836
6. •
   (dialect, no longer used) A hedgehog.
7. •
   (no longer used) A mischievous elf supposed sometimes to take the form of a hedgehog.

   • We'll dress [them] like urchins, ouphes, and fairies. — 1597