activation energy activation energy /ˌækˈtɪveɪʃən ˈɛnərdʒi/

noun

1. () The energy that an atomic system must acquire before a process (such as an emission or reaction) can occur  ( energy of activation , activation energy )
   the energy that an atomic system must acquire before a process (such as an emission or reaction) can occur
    Catalysts are said to reduce the energy of activation during the transition phase of a reaction
   catalysts are said to reduce the energy of activation during the transition phase of a reaction