diffident
adj. 羞怯的;缺乏自信的;谦虚谨慎的
例句
John was as bouncy and ebullient as Helen was diffident and reserved.
约翰活泼、热情;而海伦却羞怯、矜持。
《柯林斯英汉双解大词典》
He was modest and diffident about his own success.
他很谦虚,不愿谈及自己的成功。
《牛津词典》
Speak out, my boy--don't be diffident.
说出来吧,孩子——别害怕。