乘虛而入 chéng xū ér rù

DEFINITIONS

  1. to enter by exploiting a weak spot (idiom); to take advantage of a lapse

CHARACTERS

乘 chéng
HSK 4
ride, ascend; avail oneself of; numerary adjunct for vehicles
虛 xū false, worthless; empty, hollow
而 ér
HSK 3
and; and then; and yet; but
入 rù
HSK 4
enter, come in(to), join