The phrase "had sized up" typically means to observe, evaluate, or appraise someone or something. There are a variety of synonyms for this term that can convey similar meanings, such as assessed, analyzed, scrutinized, evaluated, judged, estimated, gauged, weighed, and measured. Each of these words implies a careful and thoughtful examination of a person or situation, often with the goal of making a decision or forming an opinion. Using synonyms for "had sized up" can help to enhance writing by providing more descriptive language and avoiding repetitive phrasing.