The phrase "in gut" has various synonyms that express the same meaning, such as "intuitive," "instinctive," and "spontaneous." It is used to describe a feeling that comes from within, without any rationalization or logical reasoning. Other words that can be used as synonyms for "in gut" include "visceral," "gut-level," and "deep-seated." Consequently, this phrase is often used to describe a personal reaction to a situation, decision or idea when you feel confident in an immediate response or decision without overtly thinking things over. Whether you use the phrase "in gut" or one of its synonyms, the meaning remains the same - it's all about a feeling within.