When some of the energy required for a reaction is provided by a preceding exothermic chemical reaction there is said to be chemical activation. For example, in the scheme:
C01017-1.png
C01017-2.png
some or all of the energy required for X to decompose is provided by the first reaction.
Source:
PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 158 (https://doi.org/10.1351/pac199668010149)