noun

a mark, blemish, or other imperfection which mars a substance or object.

a flaw in the glass

defect,blemish,fault,imperfection,deficiency,weakness,weak spot/point,inadequacy,shortcoming,limitation,failing,foible,shortfall,insufficiency,lack,want,omission,snag,kink,deformity,taint,crack,fissure,break,tear,split,scratch,chip,fracture,spot,mistake,error,bug,virus,glitch,gremlin

verb

mar, weaken, or invalidate (something).

the computer game was flawed by poor programming