The word "theftful" does not exist in the English language. However, if we consider the term "theft", which refers to the act of taking someone else's property without permission, we can explore synonyms that can be used in its place. Some common synonyms for theft include stealing, larceny, robbery, pilfering, thievery, embezzlement, appropriation, and burglary. These words capture different aspects and degrees of illegal or unauthorized taking of property. It is crucial to use appropriate synonyms in order to convey a precise meaning and enhance communication.