The mass of an atom. / (proscribed) atomic weight; the average mass of atoms of an element.

(music) Lacking a tonal center or key. / (linguistics) Not tonal, lacking tones.

(transitive, intransitive) To make reparation, compensation, amends or satisfaction for an offence, crime, mistake or deficiency.

(quantum mechanics, chemistry) A mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus.

a type of island consisting of a ribbon reef that nearly or entirely surrounds a lagoon and supports, in most cases, one to many islets on the reef platform. Atolls have a unique geology, so not all islands with a reef and a lagoon are atolls

An instrument for reducing a liquid to spray or vapor for disinfecting, cooling, medical use or perfume spraying.

(physics) A nucleus of an atom; consisting of protons and neutrons, surrounded by an electron cloud.

(chemistry) A unit of mass equal to 1/12 the mass of an atom of the ¹²C isotope of carbon.

(countable, military) A nuclear weapon that obtains its destructive energy from nuclear fission.

(uncommon) Nuclear winter.