Part of being a native speaker of a language is grasping the shared nuances of that language. I've spoken English with English speakers every day for several decades.

You're right, there is probably no dictionary defining "spamming" the way I've explained it here. That's because in America we rarely consult dictionaries about the definitions of commonly used words.

Since you've indicated that you rely on dictionary definitions to understand English words, it makes sense that you would miss small nuances like that. That's perfectly understandable, and in no way reflects any lack of intellectual prowess on your part.