A widow is a woman whose spouse has died. The word usually refers to a bereaved woman who has not remarried. Widower is simply the male equivalent of widow. It refers to a man who has lost his spouse and has not remarried. The words come from Old English, where widow was wydewe and widower was wydewa.
Examples
The latest volley took place recently when McNamee’s widow sued her deceased husband’s business partners and an Elgin attorney. [Chicago Tribune]
Patrick, a widower, age 88, has been living in a retirement home for two years. [Canada.com]
The widow of a man killed on his 25th wedding anniversary has hugged the mother of the man whose culpable driving killed him. [Herald Sun]
He died at St Columba’s, unaware that he was a widower. [Scotsman]