He sang loudly and unabashedly even though everyone was staring at him.

unabashedly 是由前缀 un-（表示"不"）和形容词 abashed（"窘迫的、羞愧的"）加上副词后缀 -ly 构成的。abashed 来自动词 abash（"使窘迫"），所以 unabashed 意思是"不感到窘迫的"，unabashedly 作为副词表示"毫不羞怯地、坦然地"。