略知皮毛[lüè zhī pí máo]
词典have only a superficial understanding：略知皮毛。
略知皮毛的反义词
have only a superficial understanding (of a subject)
1. 他对法语只是略知皮毛。 He had only a rudimentary knowledge of French.
2. 略知皮毛者总爱反复谈论那点皮毛。 People who knows a little always like to talk the little.