Particle dispersion behaviour in a solid liquid fluidised system leads to interesting outcomes such as mixing and segregation which are often quantified by an empirical dispersion coefficient. The present study aims at providing a better estimation of particle dispersion behaviour from a fundamental definition analogous to diffusion coefficient. By tracking a tracer particle using high speed image analysis, fluctuating velocity components (V-i/) were determined in a solid-liquid fluidised bed comprising glass particles (d(s) = 8 mm. rho(s) = 2230 kg m(-3)) and water as a fluidising medium. Both inter-particle and partide-wall collisions were determined from the time varying jerk data. The particle mean-free path (lambda) was then estimated as a distance between two successive peaks in the jerk profile. Finally, dispersion efficient D was computed based on the product of and V. Estimated dispersion coefficients were compared with the available correlations and reasonable agreement was obtained. (C) 2020 Elsevier B.V. All rights reserved.