weak interaction

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One of the four fundamental interactions of nature, mediated by the intermediate vector bosons and acting on leptons and quarks. It is responsible for the decay of many hadrons, for the beta decay of nuclei, and for the interactions of neutrinos. The weak interaction is weaker than the strong and electromagnetic interactions, but stronger than the gravitational interaction.
• noun An instance of this interaction.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics The fundamental interaction responsible for the weak nuclear force.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (physics) an interaction between elementary particles involving neutrinos or antineutrinos that is responsible for certain kinds of radioactive decay; mediated by intermediate vector bosons