What does a horse at a gate have to do with breaking and entering? Let’s find out.
The Chinese word 闯入 [闖入] means to break into, to barge into, to intrude (into), to charge in, or to gate-crash. It’s pronounced chuǎngrù in Mandarin and cong2 jap6 in Cantonese. It’s also found in Japanese as 闖入 (chinnyū), meaning instrusion or forced entry [source].
What’s that all got to do with horses and gates?
Well, the first character, 闯 [闖] means to rush, to charge, to dash, to break through, to temper oneself (through battling hardships) in Mandarin and Cantonese [source 1], [source 2], and to rush in or burst in in Japanese [source]. It’s made up of the characters 门 [門] (mén / mun4 / mon), meaning gate, door, entrance, and 马 [馬] (mǎ / maa5 / ba), meaning horse. It’s an ideogrammic compound that could be interpreted as a horse rushing through a gate [source].
The second character, 入 means to enter, go into, join and various other things in Chinese, and to enter or insert and so on in Japanese [source].
The character 闯 [闖] also appears in words such as:
- 闯荡 [闖盪] (chuǎngdàng / cong2 dong6) = to leave home to work, to get away from home, to wander the world, well-traveled, adventurous (Mandarin & Cantonese)
- 闯祸 [闖禍] (chuǎngguò / cong2 wo6) = to get into trouble, to suffer disaster, to suffer an accident, to induce or cause a disaster or misfortune (Mandarin / Cantonese)
- 私闯 [私闖] (sīchuǎng / si1 cong2) = to enter (a place) without permission, to intrude into (Mandarin / Cantonese)
- 闯关者 [闖關者] (chuǎngguānzhě / cong2 gwaan1 ze2) = gate-crasher, person who crashes through a barrier (Mandarin / Cantonese)
- 闖入者 (chinnyūsha) = to intruder or trespasser (Japanese)
- 闖入する (chinnyū suru) = to intrude or break in (Japanese)
Sources: Wiktionary, MDBG, CC-Canto, jisho

One useful translation exercise here is to keep the whole English sentence alongside 闖入, rather than memorising “break into” as a fixed equivalent. “Break into a room” and “break into song” use the same English words but describe quite different actions; the horse-and-gate image helps with the first sense, but would mislead a learner translating the second literally.
The character breakdown is also a good memory aid without being a pronunciation rule: 門 (mun4) and 馬 (maa5) do not combine their sounds to produce 闖 (cong2). Keeping the compound, its Jyutping and the audio together makes that distinction much clearer. A short example sentence for each of the listed compounds would be a helpful next step for learners moving from recognising characters to choosing words in conversation.
Disclosure: I am posting on behalf of EnglishToCantonese.com, an English-to-Cantonese translation tool with Jyutping and pronunciation audio.