劍橋詞典

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
內(nèi)涂層，底涂層；底漆，底層涂料
Those red walls will probably need two undercoats. 那些紅色墻壁可能需要刷兩層底漆。
比較
topcoat 返回 undercoat