'Widow' in the Bible

Then Judah told Onan, “Go in to your brother’s widow, and perform your duty as a brother-in-law [under the levirate marriage custom]; [be her husband and] raise children for [the name of] your brother.”

Onan knew that the child (heir) would not be his [but his dead brother’s]; so whenever he lay with his brother’s widow, he spilled his seed on the ground [to prevent conception], so that he would not give a child to his brother.

Then said Judah to Tamar his daughter in law, Remain a widow at thy father's house, till Shelah my son be grown: for he said, Lest peradventure he die also, as his brethren did. And Tamar went and dwelt in her father's house.