A collision between two molecules in which the amount of energy transferred from one to the other is not large compared to kB.T (kB is the Boltzmann constant and T the absolute temperature).
See: Boltzmann constant, strong collision
Source:
PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 191 (https://doi.org/10.1351/pac199668010149)