In the context of molecular dynamics, a force field is a more loosely defined term and refers to the functional form and parameter sets used to describe the interactions (potential, forces) within a system of particles (atoms or similarly sized objects). It is independent of the system's configuration, and is not a numerical field as in the above context. A force field can be empirical, derived from higher-level modelling (e.g. quantum chemical studies) or even heuristic.
In science fiction and fantasy literature, a force field is a physical barrier made up of energy to protect a person or object from attacks or intrusions.