趁虛而入 [－虚－－]

Jyutping can3 heoi1 ji4 jap6
Pinyin chèn xū ér rù

Definitions (Wiktionary)
  1. phrase, idiomatic
    to enter or invade by exploiting of one's opponent's unpreparedness or weakness; to break through a weak point or advance when one's opponent is off guard
    (syn.) 乘虛而入, 乘虚而入
Definitions (Kaifangcidian)
  1. （沒有對應漢語詞彙）