Bat an eye is an informal expression that refers to showing no visible reaction or surprise to something that is unusual or unexpected. This expression can be substituted with different synonyms to convey the same meaning, such as remain unfazed, show no emotion, stay nonchalant, maintain composure, keep a poker face, or exhibit self-control. These synonyms are ideal for situations where one wants to appear unaffected by a circumstance that might otherwise be shocking or unsettling. Using these alternatives can help one express themselves more creatively and add variety to their vocabulary, making their speech more compelling and engaging.