Grounds and Undercoat

Grounds noun - Your basis for belief or disbelief; knowledge on which to base belief.

Undercoat is a synonym for grounds. In some cases you can use "Undercoat" instead the word "Grounds" as a noun or a verb.

Undercoat noun - The first or preliminary coat of paint or size applied to a surface.

Grounds is a synonym for undercoat. Sometimes you can replace term "Grounds" with "Undercoat", this nouns are similar.