Final answer:
The term 'Weakened' does not describe a casualty deductible for tax purposes as it suggests a gradual process, unlike the sudden and unexpected nature of deductible casualties.
Step-by-step explanation:
The term that does NOT describe a casualty that could be deductible for tax purposes is 'Weakened'. For a casualty loss to be deductible, it must be the result of a sudden, unexpected, and unusual event. 'Sudden' implies that the event occurred abruptly, 'unexpected' means it was not anticipated, and 'unusual' indicates that it was not a day-to-day occurrence. The term 'weakened' does not fit within these parameters, as it suggests a gradual process rather than a sudden event.