The Collaborative International Dictionary of English v.0.48:

Pebble \Peb"ble\, n. [AS. papolst[=a]n; cf. L. papula pimple,
   mote. See Stone.]
   1. A small roundish piece of stone; especially, a stone worn
      and rounded by the action of water; a pebblestone. "The
      pebbles on the hungry beach." --Shak.
      [1913 Webster]

            As children gathering pebbles on the shore.
                                                  --Milton.
      [1913 Webster]

   2. Transparent and colorless rock crystal; as, Brazilian
      pebble; -- so called by opticians.
      [1913 Webster]

   Pebble powder, slow-burning gunpowder, in large cubical
      grains.

   Scotch pebble, varieties of quartz, as agate, chalcedony,
      etc., obtained from cavities in amygdaloid.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pebble \Peb"ble\, v. t. [imp. & p. p. Pebbled; p. pr. & vb. n.
   Pebbling.]
   To grain (leather) so as to produce a surface covered with
   small rounded prominences.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pebble
    n 1: a small smooth rounded rock

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

Pebble

   A polymorphic language.

   ["A Kernel Language for Abstract Data Types and Modules",
   R.M. Burstall & B. Lampson, in Semantics of Data Types, LNCS
   173, Springer 1984].

   (1995-01-26)