plus-one

American  

[pluhs-wuhn] / ˈplʌsˈwʌn /

Or plus one

noun

1. a person who accompanies someone to a party or other event when the invitation allows the invited guest to bring another person.

   I phoned Tom to ask if he would be my plus-one at the gala.

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plus-one British  

noun

1. informal a person who accompanies an invited person to a social function

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Etymology

Origin of plus-one

First recorded in 1970–75

Example Sentences

I was a plus-one, so naturally I stood in line on an unusually hot November day holding a cake I didn’t make.

From The Wall Street Journal

Yes, the CEO was the HR chief’s “plus-one” that night at the concert.

From Los Angeles Times

Not so at the lavish evenings hosted by law firms, where I happily tagged along as the plus-one of first- and second-year associates.

From The Wall Street Journal

In the win against Arsenal earlier this season, Liverpool started the match by keeping a 'plus-one' in their defensive line.

From BBC

Or, as Gala puts it: “It was infinitely more satisfying to be somebody rather than somebody’s plus-one.”

From Los Angeles Times