As a former plant nursery employee, it’s soil when it’s in a container, and dirt once it hits the floor.

Dirt is the accumulation of everything that used to be alive since the beginnings of life on this planet, broken down over millenia and some of it also including inorganic materials, stacked on top of each other and compressed.

baby don’t hurt me, don’t hurt me no more

Stuff that hasn’t undergone pedogenesis. If it’s under your fingernails or on your car, you can call it dirt ;)