transition coordinate

https://doi.org/10.1351/goldbook.T06455
The reaction coordinate at the transition state corresponding to a vibration with an imaginary frequency. Motion along it in the two opposite senses leads towards the reactants or towards the products.
Source:
PAC, 1994, 66, 117. 'Biochemical engineering in biotechnology (Technical Report)' on page 117 (https://doi.org/10.1351/pac199466010117)