be a synonym/byword for/of =be synonymous with
e.g.
说到圣诞节，人们常常会想到充满节日氛围的装饰，礼物和圣诞老人。
Christmas has always been synonymous with festive decorations, gifts and Santa Claus.
马克龙总统不想人们将他的政策改变看成是对街头抗议的妥协。
The last thing President Macron want is to have his u-turn seen as synonymous with a climb-down.
