If I were to cross breed two different plants together

If I were to cross breed two different plants together, would the offspring be "genetically modified" plants?

They would be "genetically modified" in the general sense of the phrase, but not by the standard *industry* definition of the phrase.

"Genetic modification" implies transgenic. Which means it has undergone gene transformation via Agrobacterium or a gene gun.

(Of course the definition is also slightly different in animals, but let's not go there.)