"Flat one back" can be replaced by a range of synonyms. Some of these synonyms are: bow down, slump, hunch, droop, stoop, sag, wilt, and languish. Each of these synonyms represents a different degree of physical or emotional exhaustion and defeat. For example, "bow down" connotes defeat and submission, while "slump" conveys a sense of listlessness and fatigue. Similarly, "languish" suggests a state of yearning and unfulfilled desire, while "hunch" suggests a defensive posture and a sense of being under attack. These synonyms can be used in various contexts from describing a person's physical posture to signifying a general sense of discouragement and disappointment.