UNDERCOAT Meaning of UNDERCOAT in English un ‧ der ‧ coat /ˈʌndəkəʊt $ -dərkoʊt/ BrE AmE noun [countable] a layer of paint that you put onto a surface before you put the final layer on ⇨ topcoat Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012