4. (noun)fusion, nuclear fusion, nuclear fusion reaction a nuclear reaction in which nuclei combine to form more massive nuclei with the simultaneous release of energy Synonyms: merger, nuclear fusionreaction, unification, optical fusion, coalition, fusion, nuclear fusion, spinalfusion
6. (noun)fusion, spinal fusion correction of an unstable part of the spine by joining two or more vertebrae; usually done surgically but sometimes done by traction or immobilization Synonyms: merger, nuclear fusionreaction, unification, optical fusion, coalition, fusion, nuclear fusion, spinalfusion
Synonyms and Antonyms of fusion 
