against是动词，是反对的意思。
against
prep.
反对; 为…预备, 为…准备, 防备; (概念上)按照, 参照, 与…相对; 倚着, 靠在
释义
prep.
①in opposition to
反对
②the fight against crime
打击犯罪的斗争
③arguing against the ordination of women
为反对授予妇女基督教圣职而争论
④you've turned her against me
你让她和我作对起来了
⑤he decided against immediate publication
他决定不马上出版
⑥swimming against the tide.
逆流游泳。
用法如下
（1)表示“反对”、“违背”之意。如：
①They are strongly against the idea.
他们强烈反对这个意见。
②Are you for or against my plan?
对于我的计划你是赞成还是反对？
③What have you done is against the law.
你所做的事情是违法的。
④Jane married Jack against her own will.
简与杰克结婚，违背了自己的意愿。
（2）表示“撞击”、“碰着”之意。如：
①The rain was beating the windows.
雨点拍打着窗户。
②Tom hit his head against a tree in the dark.
黑暗中汤姆的头撞在一棵树上。
（3）表示“倚在”、“紧靠”之意。如：
①Place the ladder against the wall.
把梯子靠在墙上。
（4）表示“逆着”的意思。如：
①We are sailing against the wind.
(with the wind表示“顺风”)我们的船正在逆风行驶。
（5）表示“衬托”、“相映”、“对照”之意。如：
①Red flags stand out brightly against the blue sky.
红旗在蓝天的衬托下显得分外鲜艳。
（6）表示“防备”、“预防”之意。如：
①People are warned against pick-pockets.
人们得到告诫，要谨防扒手。