The Collaborative International Dictionary of English v.0.48:

Urchin \Ur"chin\ ([^u]"ch[i^]n), n. [OE. urchon, irchon, a
   hedgehog, OF. ire[,c]on, eri[,c]on, heri[,c]on, herichon, F.
   h['e]risson, a derivative fr. L. ericius, from er a hedgehog,
   for her; akin to Gr. chh`r. Cf. Herisson.]
   [1913 Webster]
   1. (Zool.) A hedgehog.
      [1913 Webster]

   2. (Zool.) A sea urchin. See Sea urchin.
      [1913 Webster]

   3. A mischievous elf supposed sometimes to take the form a
      hedgehog. "We 'll dress [them] like urchins, ouphes, and
      fairies." --Shak.
      [1913 Webster]

   4. A pert or roguish child; -- now commonly used only of a
      boy.
      [1913 Webster]

            And the urchins that stand with their thievish eyes
            Forever on watch ran off each with a prize. --W.
                                                  Howitt.
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            You did indeed dissemble, you urchin you; but
            where's the girl that won't dissemble for an
            husband?                              --Goldsmith.
      [1913 Webster]

   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. --Knight.
      [1913 Webster]

   Urchin fish (Zool.), a diodon.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Urchin \Ur"chin\, a.
   Rough; pricking; piercing. [R.] "Helping all urchin blasts."
   --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

urchin
    n 1: poor and often mischievous city child

The Free On-line Dictionary of Computing (19 January 2023):

munchkin
urchin

   /muhnch'kin/ [Squeaky-voiced little people in L. Frank Baum's
   "The Wizard of Oz"] A teenage-or-younger micro enthusiast
   hacking BASIC or something else equally constricted.  A term
   of mild derision - munchkins are annoying but some grow up
   to be hackers after passing through a larval stage.  The
   term urchin is also used.  See also wannabee, bitty box.

   [Jargon File]


The Jargon File (version 4.4.7, 29 Dec 2003):

urchin
 n.

    See munchkin.