Manslaughter is the crime of killing someone against the law, but not as murder. The death was unlawful, yet the killer did not set out to murder — a fight that went too far, a moment of lost control, or driving so carelessly that someone died. In English and American law it is still very serious, but the law treats it as lighter than murder because there was no plan to kill, or the killing was not fully intended. Lawyers, news reports, and courts use it; it is not a casual word. Though actually, the man here is the old word for “a person,” not “an adult male,” and slaughter is “killing.” Different countries draw the line in different places, so the Chinese legal name will not match the English one tick for tick.