cold fusion

Short definition from Wiktionary

Noun

1. 1
   Nuclear fusion at or near room temperature: A hypothetical and now discredited form of nuclear fusion involving electrolysis of heavy water.
2. 2
   Nuclear fusion at or near room temperature: Muon-catalyzed fusion
3. 3
   A method of synthesizing superheavy elements, where the product nucleus has a relatively low excitation energy of ~10 to 20 MeV.