剑桥词典a first layer of paint that is put on a surface in order to improve the appearance of the final one, or the paint used for this 内涂层，底涂层；底漆，底层涂料 Those red walls will probably need two undercoats. 那些红色墙壁可能需要刷两层底漆。 比较topcoat 返回 undercoat