When we talk about "broad lines," we are usually referring to general or overarching ideas that encompass a large scope. However, there are several synonyms that can be used to convey this same concept using different language. For instance, "general outline," "big picture," "wide-ranging concepts," "wide scope," or "broad overview" can all be used in place of "broad lines." Additionally, words like "generalized," "comprehensive," or "all-encompassing" can also be used as synonyms for broad lines to indicate a broad and sweeping understanding of a given subject. By using different synonyms for "broad lines," we can add richness and variety to our language while still conveying the same central idea.