any of the patterned sets of vertical bars of varying widths imprinted on consumer products, mail, etc. and containing coded information that can be read by a computerized scanner
See bar code in American Heritage Dictionary 4
noun
A series of vertical bars of varying widths, in which each of the digits zero through nine are represented by a different pattern of bars that can be read by a laser scanner. The bars are commonly found on consumer products and are used especially for inventory control.