1. A small roundish stone or bowlder; especially, a stone worn and rounded by the action of water; a pebblestone. The pebbles on the hungry beach. As children gathering pebbles on the shore. (milton)
2. Transparent and colourless rock crystal; as, Brazilian pebble; so called by opticians. Pebble powder, slow-burning gunpowder, in large cubical grains. Scotch pebble, varieties of quartz, as agate, chalcedony, etc, obtained from cavities in amygdaloid.
Origin: AS. Papolstan; cf. L. Papula pimple, mote. See Stone.