Intestableness refers to the state of being legally unable to make a valid will. Synonyms for this phrase can include "testamentary incapacity," "incompetence," and "lack of testamentary capacity." These terms suggest that the individual lacks the mental or legal capacity necessary to create a binding will, either due to mental illness, developmental disability, or simply a lack of understanding of the legal requirements for creating a will. Other related phrases might include "lack of testamentary intent," "undue influence," or "duress," which refer to situations where the individual may have had some form of coercion placed upon them that prevented them from creating a valid will.