「家内」 (Kanai) is a humble term used by a man to refer to his own wife to others. It's often used when speaking to someone outside the family. It implies "my wife who stays at home." For example: 私の家内は料理が上手です。(My wife is good at cooking.)

自分の妻を他の人に話すときに使う、謙譲語の表現です。例：うちの家内。