The phrase "withering away" typically refers to a gradual and weakening decline of something over time. Some synonyms for this phrase might include languishing, deteriorating, decaying, or wasting away. Each of these terms implies a slow and steady loss of vitality or strength, whether it be physical, emotional, or intellectual. Other possibilities might include phrases like "fading into obscurity," "shrinking into nothingness," or "melting away like snow in the sun." Regardless of the specific words used, the underlying sense of a slow, painful decline is common to all these phrases, and they each evoke a feeling of sadness, loss, or weariness.