守寡 means 'to remain a widow' — a woman who does not remarry after her husband dies. It's a separable verb (离合词): the verb 守 and the object 寡 can split when you add duration or measure words, like 守了十年寡 ('stayed a widow for ten years'). The word carries traditional cultural weight — in historical China, widow chastity was a virtue, and the term reflects that social expectation. You cannot use it for men (a widower is 鳏夫, guānfū).