Spiteful describes someone who is nasty on purpose, wanting to hurt or upset another person — and the key word is 'on purpose'. A spiteful act is not careless or thoughtless; the person chose it, and the hurting was the point. It is often small and mean rather than big and violent: telling a secret you promised to keep, saying the one sentence you know will land, leaving someone off the invitation list, breaking something the other person loved. That smallness is important — English speakers feel spiteful as a petty, low kind of nastiness, the sort that comes from wounded pride or old jealousy. So the word carries real disapproval; you are not just describing a person, you are judging them. It works on words, acts and people alike: a spiteful remark, a spiteful thing to do, a spiteful old neighbour. There is a slight extra flavour worth knowing: spiteful often means the person is hurting themselves too, or gaining nothing, just so the other one suffers — 'she sold the house cheap out of spite'. Compare it with the plain noun spite, which is the feeling, and the phrase 'in spite of', which looks the same but means something completely different (= although).