Graph pebbling is a one-player graph game in which a configuration assigns a nonnegative integer number of pebbles to each graph vertex. A pebbling move removes two pebbles from one vertex and places one pebble on an adjacent vertex, with the other pebble discarded in transit.
A configuration is said to be root-solvable for a vertex 
if a sequence of pebbling moves
can place at least one pebble on 
. The least number of pebbles such that every configuration
of that size is root-solvable for every choice of 
is the pebbling number.
Graph pebbling should not be confused with the pebble game used in sparse-graph and rigidity algorithms, which uses pebbles as markers for certifying sparsity rather than as consumable resources.
