(physics) an interaction between elementary particles involving neutrinos or antineutrinos that is responsible for certain kinds of radioactive decay; mediated by intermediate vector bosons
(a) One of the fundamental forces of nature. Its most famous manifestation is in -decay; it is also involved in some radioactive decays of nuclei, and neutrino interactions. [D89] (b) A short-range nuclear force responsible for radioactivity and for the decay of certain unstable nuclei, e.g., - + = + e, which is so called because it occurs at a rate slower than that of the strong interaction by a factor of about 10-13 (see Interactions). [H76] (c) Interactions with a typical range of about 1/100 the size of an atomic nucleus which are responsible for the beta decay of some kinds of an atomic nuclei. Neutrinos are subject to only the weak interactions and the much weaker force of gravity. [G97
The interaction responsible for all processes in which flavor changes, hence for the instability of heavy quarks and leptons, and particles that contain them. Weak interactions that do not change flavor (or charge) have also been observed.