plus one
noun [ C usually singular ] uk/ˌplʌs ˈwʌn/ us/ˌplʌs ˈwʌn/
（尤指当请柬说明可以邀请一名同伴参加时，带领参加晚会或活动的）同伴
a person that you take to a party or other event, usually when the invitation says that you can bring one other person with you
She asked Martin to be her plus one at the benefit. 她请马汀陪同参加慈善活动。