noun Date: circa 1942 a unit of mass for expressing masses of atoms, molecules, or nuclear particles equal to 1/12 the mass of a single atom of the most abundant carbon isotope 12 C
ATOMIC MASS UNIT
Meaning of ATOMIC MASS UNIT in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012