a person's partner in marriage
"After twenty years together, they finally decided to tie the knot and make each other their legal spouse."
A person in a marriage or marital relationship.
"After twenty years, she finally introduced her new spouse to her entire family."
In plain English: A spouse is your husband or wife, meaning the person you are legally married to.
"Her spouse surprised her with dinner on their anniversary."
Usage: Use spouse to refer specifically to your husband, wife, or civil partner within the context of an existing legal union. It is more formal than terms like boyfriend, girlfriend, or significant other and does not apply to unmarried partners unless they are legally married.
To wed; to espouse.
"After years of dating, they decided to finally spouse each other in a small ceremony."
The word "spouse" entered Middle English from the Anglo-Norman and Old French forms of a Latin term meaning bridegroom or bride, which originally referred specifically to someone who had made vows. It eventually replaced the native Old English word for partner but now covers both husbands and wives in modern usage.