I'm listening to "Save yourself" from Birdy. She says: "Look at what we have become, empty hearts that spare no one" What does "spare no one" mean? I've searched in dictionary but I haven't find anything.
It is always hard to interpret verse or song, where brevity is often valued over clarity, metaphor and other figures of speech are common. and meaning may be distorted for the sake of rhythm or rhyme.
That said, I take this to mean that "spare" (a verb here) is used in the sense of "show mercy to" or "refrain from attacking" or "refrain from harming or destroying" and so over all, the line says that "we" have become emotionless or uncaring or loveless beings who attack or destroy everyone around them. "empty hearts" is a metaphor, using the heart to stand for the seat of emotion or caring or perhaps love, and saying that "we" lack those qualities.