Source : Webster's Revised Unabridged Dictionary (1913)

Pear \Pear\ (p[^a]r), n. [OE. pere, AS. peru, L. pirum: cf. F.
   poire. Cf. {Perry}.] (Bot.)
   The fleshy pome, or fruit, of a rosaceous tree ({Pyrus
   communis}), cultivated in many varieties in temperate
   climates; also, the tree which bears this fruit. See {Pear
   family}, below.

   {Pear blight}.
   (a) (Bot.) A name of two distinct diseases of pear trees,
       both causing a destruction of the branches, viz., that
       caused by a minute insect ({Xyleborus pyri}), and that
       caused by the freezing of the sap in winter. --A. J.
       Downing.
   (b) (Zo["o]l.) A very small beetle ({Xyleborus pyri}) whose
       larv[ae] bore in the twigs of pear trees and cause them
       to wither.

   {Pear family} (Bot.), a suborder of rosaceous plants
      ({Pome[ae]}), characterized by the calyx tube becoming
      fleshy in fruit, and, combined with the ovaries, forming a
      pome. It includes the apple, pear, quince, service berry,
      and hawthorn.

   {Pear gauge} (Physics), a kind of gauge for measuring the
      exhaustion of an air-pump receiver; -- so called because
      consisting in part of a pear-shaped glass vessel.

   {Pear shell} (Zo["o]l.), any marine gastropod shell of the
      genus {Pyrula}, native of tropical seas; -- so called from
      the shape.

   {Pear slug} (Zo["o]l.), the larva of a sawfly which is very
      injurious to the foliage of the pear tree.

Source : WordNet®

pear blight
     n : a disease blackening the leaves of pear and apple trees
         [syn: {fire blight}]