“Gist” means “essence,” “main part.” But expressions like “the gist of it” are most often used in modern speech to more vaguely refer to the general sense of a matter: “I didn’t understand everything in the chapter, but I got the gist of it.” This broadened sense will offend few people, but it’s more of a problem if you replace this unusual word with a more familiar one like “just” or “jest.”
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