weak-kneed
adjective [ after verb ] uk/ˌwiːkˈniːd/ us/ˌwiːkˈniːd/
informal disapproving软弱的，不勇敢的；不坚定的
not brave or determined enough to defend your beliefs against others
Instead of defending traditional values, the church frequently seems weak-kneed and irresolute. 教会不但没有去维护传统的价值观，反而常常表现得软弱且犹豫不决。
（强烈的情感作用下）感到软弱无力的，膝盖发软的
made to feel weak and likely to fall by emotion
She stood dazed and weak-kneed beside the coffin. 她站在棺材旁边，头晕目眩，膝盖发软。