at. wt.

Noun

atomic weight (plural atomic weights)

1. Former term for the more specific relative atomic mass.
   • The equivalent weight of an element or compound is that weight equivalent in reactive power to one atomic weight of hydrogen.1922, Leicester F. Hamilton, Calculations of Analytical Chemistry, page 38
2. A term used to represent the mean relative atomic mass of an element in nature, as distinct from the relative atomic mass of a single isotope.