"Catch unaware" is a phrase used to describe the act of surprising or shocking someone. There are a number of synonyms that can be used to replace this phrase, each with their own unique connotations. For instance, "take aback" or "startle" can be used to imply a sudden shock or surprise. Similarly, "blindside" or "ambush" can be used to suggest an unexpected attack or incident. Other synonyms that can be used in place of "catch unaware" include "take by surprise," "catch off guard," and "throw off balance." No matter which synonym is used, it is important to consider the context of the situation and choose a word that accurately describes the intended effect.