The phrase "most giveaway" typically means something that is obvious or easy to figure out. Synonyms for this phrase include "blatant," "clear," "evident," "transparent," "open," "overt," "apparent," "unmistakable," "plain," and "self-evident." These words all describe something that is easily noticed or understood, without much effort or thought required. Using synonyms can help to add variety and nuance to your writing, and can also help you avoid repeating the same word over and over again. When looking for synonyms, consider the context in which you're using the word, and choose words that accurately convey your intended meaning.