Question

Can the intermixing of two solids be termed as diffusion

Answer 1

No the intermixing of two solids in this case can't be termed as diffusion as in diffusion there is a movements of particles from a gradient and in this case take two solids (say) Iron filings and sulphur mixing then by physical methods or by chemical method would not result and result in a new compound respectively. But in those cases also neither there is exchange in particles not there is a change in the gradient.

Answer 2

Particles of solids are held together by strong inter-molecular forces. ... Therefore, the intermixing of two solids cannot be termed as diffusion.