the revealing of a painting or part of a painting that has been covered over by a later painting
2.
the part of a painting thus revealed
Word origin
C20: Italian, literally: repentance
pentimento in American English
(ˌpɛntəˈmɛntoʊ)
noun
1. Art
the emergence of lines, images, etc. in a painting that become visible as oil paint grows transparent with age, thus revealing the artist's earlier ideas