diffident
adj
~ (about sth) not having or showing much belief in one's own abilities; lacking self-confidence 对自己的能力缺乏信心的; 露出怯态的; 缺乏自信的
an able but diffident young student 能干但缺乏自信的青年学生
Don't be so diffident about your talents. 别对自己的才能如此缺乏信心.
One day, he went to an exclusive shop in London and asked for 'Myrolite', the shop assistant looked puzzled and Harry repeated the word, slowly stressing each syllable.