prop·a·ga·tion 
(prŏp′ə-gāshən)
(prŏp′ə-gāshən)n.
1. Multiplication or increase, as by natural reproduction.
2. The process of spreading to a larger area or greater number; dissemination.
3. Physics The act or process of propagating, especially the process by which a disturbance, such as the motion of electromagnetic or sound waves, is transmitted through a medium such as air or water.
prop′a·gation·al adj.