The word 'addlebrained' is an unusual term, sometimes used to describe someone who is confused, disoriented or scatter-brained. Some antonyms to this word could be focused, alert, sharp, quick-witted, attentive, and intelligent. These words imply qualities in a person that are the opposite of addle-brained. They suggest that someone who is focused, for example, is not easily distracted, while someone who is alert is vigilant and observant. Similarly, someone who is sharp or quick-witted is able to come up with clever solutions and react quickly under pressure. In essence, these antonyms suggest traits of a capable and intelligent individual.