A path taken by a reaction system over potential-energy (reaction) surface or a diagram or mathematical description that represents that path. A trajectory can also be called a reaction path.
Source:
PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 189 (https://doi.org/10.1351/pac199668010149)