"Flathats" is not a widely-used term, and therefore, not many synonyms exist for this word. However, "flathat" often refers to someone who is perceived as an inexperienced or naive person, particularly within a specific field, such as sports or politics. Synonyms for "flathat" could include "rookie," "amateur," "novice," or "greenhorn." These words describe individuals who lack experience or skill, and are often used in a derogatory manner. Alternatively, one could use the phrase "newcomer" or "neophyte" to describe someone who is new to a particular field without implying any negative connotations.