expression
piling shame on top of shame; adding insult to injury
Idiomatic expression for making a shameful situation even worse by another disgraceful act.
遅刻した上に言い訳までして、恥の上塗りだった。
Not only was I late, but I made excuses on top of that, which just added to the shame.
Focuses on making someone's pain worse, while 恥の上塗り is specifically about compounding one's own shame.
Compound of 恥 (shame) + の (possessive particle) + 上塗り (adding another layer, from 上 'above' and 塗り 'coating'). The image is of applying another coat of shame over an already shameful situation.