泛泛之交

Explanation: Friendship is not deep friends. 　　Source: Song Xi "Zhuzi" Volume eighteen friends make friends, the inherent depth, if the turn of the pan and then, one by one to deal with, can not be. " 　　Examples: Or all non-communication, or P for ~ occasion. ★ Lu Xun's "Letters To Zhang Ting Qian" Thesaurus:  person whom one knows but who is not a close friend