ht night terror / nait ter/ noun a period of disturbed sleep, which a child does not remember afterwards nigra / nai r/ linea nigra nihilism / naihiliz()m/ noun the rejection of all the usual social conventions and beliefs, especially of morality and religion nihilistic / naihi listik/ adj relating to or showing a belief in nihilism nipple / nip()l/ noun 1. same as mammilla 2.