At first blush is an idiomatic expression that means to form an opinion based on a first impression. Similar phrases that can be used in place of at first blush include "at first sight," "in the beginning," "initially," or "on the surface." These phrases denote a superficial level of understanding and imply that further investigation or analysis may be needed before drawing a conclusive opinion. One can also use phrases like "at the outset," "in the early going," and "to start with" as synonyms for at first blush. These expressions are commonly used when discussing first impressions, initial thoughts or decisions about something.