The exact meaning of principal can depend upon its context. For example:
"the principal idea" or "the principal performer" — the most important
"the principal of the school" — the person in charge
"a principal of a company" — an owner or person with controlling authority
"the principal in a transaction" (as contrasted to the agent) — the person on whose behalf an agent acts
And, in Atlanta, were not only the factories for making pistols and saddles, tents and ammunition, but also the most extensive rolling mills in the South, the shops of the principal railroads and the enormous hospitals.
3.17 (3% in)
There are no more uses of "principal" in Gone with the Wind.