Bubblehead is a phrase that most people would use to describe someone who is naïve or has a lack of intelligence. However, there are many other synonyms that can be used instead of bubblehead. These synonyms include words like airhead, scatterbrain, and simpleton. Airhead refers to someone who is absent-minded, while scatterbrain describes a person who lacks focus. Simpleton is another word that can be used for someone who is intellectually challenged. Other synonyms for bubblehead include dunderhead, dimwit, and dolt. Ultimately, there are many words that can be used instead, and it's up to the speaker to choose the one that best fits the situation.