"Witnessable" is a term used to describe something that can be seen or observed by others. However, there are several synonyms for this word that can be utilized in different situations. For instance, "observable" is a broader term that can be used to describe something that can be perceived by any of the senses. "Evident" is another synonym that denotes something that is clear and obvious and requires no further proof. "Apparent" refers to something that is readily visible or can be inferred from surrounding circumstances. Lastly, "noticeable" describes something that stands out or attracts attention and can be easily seen or detected. These synonyms can help add variety to your writing and avoid repetition.