What does it mean by "transferable" in the case of a force field?

According to Wikipedia:

Functional forms and parameter sets have been defined by the developers of interatomic potentials and feature variable degrees of self-consistency and transferability. When functional forms of the potential terms vary, the parameters from one interatomic potential function can typically not be used together with another interatomic potential function.[19] In some cases, modifications can be made with minor effort, for example, between 9-6 Lennard-Jones potentials to 12-6 Lennard-Jones potentials.[9] Transfers from Buckingham potentials to harmonic potentials, or from Embedded Atom Models to harmonic potentials, on the contrary, would require many additional assumptions and may not be possible.

I haven't really understood this.

Can you give me a layman's definition of "Transferable" FF?

For example: you are given interaction potential parameters for a particular model of water that recreates the correct experimental melting point and structure of water. The model is transferred to a simulation of a supersaturated solution of $$\ce{NaCl}$$ in water, with some interaction potential of $$\ce{NaCl}$$ defined using the same functional form (e.g. Lennard-Jones). The interaction parameters between water and the ions are then defined by some combining rules. If the simulation gives useful results, the water model is said to be transferrable to simulations of supersaturated $$\ce{NaCl}$$ in water.