Natural phenomenon
A natural phenomenon is not an engineered event manufactured by humans, although it may affect them. Common examples of natural phenomena include sunrise, the weather, decomposition, free fall and erosion. Most natural phenomena, such as fog, are relatively harmless so far as humans are concerned. Various types of natural phenomena occur, including the following: ⁕Geological phenomena ⁕Meteorological phenomena ⁕Oceanographic phenomena
OR Can be defined this way
Natural phenomenon - all phenomena that are not artificial. phenomenon - any state or process known through the senses rather than by intuition or reasoning. chemical phenomenon - any natural phenomenon involving chemistry (as changes to atoms or molecules)