I've heard a single word before that means "withholding medicine from a sick person" or "withholding food from a starving person" or "refusing to alert an airplane pilot flying in the dark that he's about to crash into a mountain". The basic idea is not taking some action knowing that inaction will later lead to harm for another person.
I thought for sure there was a single word for this (and it's more malicious than "negligence"). What is it?
Perhaps you are referring to omission: a failure to do something, esp. something that one has a moral or legal obligation to do.
Synonyms: negligence, neglect, neglectfulness, dereliction, forgetfulness, oversight, default, lapse, failure.
Perhaps you have heard of sins of *o*mission, as opposed to sins of *co*mmission. People have a moral obligation to do the right thing. If they do the wrong thing, they have committed a bad act. If they fail to act when it is called for, they are to blame for what they did not do.
Are you thinking of malevolent perhaps?
Are you thinking of "malfeasance"? The first examples suggest "deprivation," and that, too, is malicious. But deprivation doesn't fit the case of not alerting someone.
