A name used poetically for Israel
But Jeshurun waxed fat, and kicked: thou art waxen fat, thou art grown thick, thou art covered with fatness; then he forsook God which made him, and lightly esteemed the Rock of his salvation. (Deuteronomy 32:15)
And he was king in Jeshurun, when the heads of the people and the tribes of Israel were gathered together. (Deuteronomy 33:5)
There is none like unto the God of Jeshurun, who rideth upon the heaven in thy help, and in his excellency on the sky. (Deuteronomy 33:26)
Thus saith the Lord that made thee, and formed thee from the womb, which will help thee; Fear not, O Jacob, my servant; and thou, Jesurun, whom I have chosen. (Isaiah 44:2)