gigaannum

noun

1. Alternative spelling of giga-annum (“gigayear, a billion years”).

   “Studies of the Earth’s processes, phenomena, and origins are unique in the physical sciences for their need to observe and measure past events over spatial and temporal scales that range from the micron and second to the astronomical unit and gigaannum.”

   “The oldest materials ever found in the Solar System occur in meteorites ~4.57 Ga (gigaannum or billion years ago) of age, marking the starting point for the condesation of the first solids in our Solar System.”