When we talk about "white knuckles", we usually refer to a state where one's grip is so tight that their knuckles become visibly white due to the pressure. However, this expression can be replaced by several synonyms that convey a similar meaning. These include terms like "clenched fists", "tight grip", "nerve-wracking", "tense", "anxiety-provoking", "fearful", and "intense". Depending on the context, any of these expressions can be used to describe a situation where someone is experiencing fear, anxiety, tension, or stress, which causes them to tense up and cling on to something tightly. Regardless of the term used, the underlying feeling is one of being on edge and uncomfortable.