significant other
compound. B2 Upper Intermediate
compound. A person's husband, wife, or romantic partner. People often use it when they don't want to state whether a couple is married, or the exact kind of relationship.
compound. A person's spouse or established romantic partner — a deliberately neutral term that avoids specifying marital status, gender, or relationship type. Common on forms and in polite or inclusive contexts.
You're welcome to bring your significant other to the party.
The invitation said each guest could bring a significant other, so Priya brought her girlfriend.
The company's benefits policy was rewritten to cover an employee's significant other, whether or not the couple had chosen to marry.