The Collaborative International Dictionary of English v.0.48:

Sparrow \Spar"row\, n. [OE. sparwe, AS. spearwa; akin to OHG.
   sparo, G. sperling, Icel. sp["o]rr, Dan. spurv, spurre, Sw.
   sparf, Goth. sparwa; -- originally, probably, the quiverer or
   flutterer, and akin to E. spurn. See Spurn, and cf.
   Spavin.]
   1. (Zool.) One of many species of small singing birds of the
      family Fringilligae, having conical bills, and feeding
      chiefly on seeds. Many sparrows are called also finches,
      and buntings. The common sparrow, or house sparrow, of
      Europe (Passer domesticus) is noted for its familiarity,
      its voracity, its attachment to its young, and its
      fecundity. See House sparrow, under House.
      [1913 Webster]

   Note: The following American species are well known; the
         chipping sparrow, or chippy, the sage sparrow,
         the savanna sparrow, the song sparrow, the tree
         sparrow, and the white-throated sparrow (see
         Peabody bird). See these terms under Sage,
         Savanna, etc.
         [1913 Webster]

   2. (Zool.) Any one of several small singing birds somewhat
      resembling the true sparrows in form or habits, as the
      European hedge sparrow. See under Hedge.
      [1913 Webster]

            He that doth the ravens feed,
            Yea, providently caters for the sparrow,
            Be comfort to my age!                 --Shak.
      [1913 Webster]

   Field sparrow, Fox sparrow, etc. See under Field,
      Fox, etc.

   Sparrow bill, a small nail; a castiron shoe nail; a
      sparable.

   Sparrow hawk. (Zool.)
      (a) A small European hawk (Accipiter nisus) or any of
          the allied species.
      (b) A small American falcon (Falco sparverius).
      (c) The Australian collared sparrow hawk (Accipiter
          torquatus).

   Note: The name is applied to other small hawks, as the
         European kestrel and the New Zealand quail hawk.

   Sparrow owl (Zool.), a small owl (Glaucidium passerinum)
      found both in the Old World and the New. The name is also
      applied to other species of small owls.

   Sparrow spear (Zool.), the female of the reed bunting.
      [Prov. Eng.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

sparrow
    n 1: any of several small dull-colored singing birds feeding on
         seeds or insects [syn: sparrow, true sparrow]
    2: small brownish European songbird [syn: hedge sparrow,
       sparrow, dunnock, Prunella modularis]

Easton's 1897 Bible Dictionary:

Sparrow
   Mentioned among the offerings made by the very poor. Two
   sparrows were sold for a farthing (Matt. 10:29), and five for
   two farthings (Luke 12:6). The Hebrew word thus rendered is
   _tsippor_, which properly denotes the whole family of small
   birds which feed on grain (Lev. 14:4; Ps. 84:3; 102:7). The
   Greek word of the New Testament is _strouthion_ (Matt.
   10:29-31), which is thus correctly rendered.