The Chinese words locals use to describe extra-marital affairs are of critical necessary for expats in relationships with Chinese girlfriends.  Not just when you are hanging out with your own girlfriend, but also when you’re out with all her other Chinese friends.  If your girlfriend and her friends are using the local slang, everyone will “know for sure” that her foreign boyfriend has no clue what they are talking about.  Most of the time they would be right, but after reading the Chinese Slang Blog you will know everything they are saying.  With your carefully practiced poker face, you can play stupid while her friends are carelessly divulging all their secret information or you can impress all her Chinese friends with your new Chinese slang knowledge that only a local should know.  

婚外恋-hūn wài liàn-Extramarital affair, a bit on the side (Noun)

Literal Translation-Marrige outside love

他已经结婚了，但是他有婚外恋。

tā yǐjīng jiéhūn le，dànshì tā yǒu hūnwàiliàn。

He is a married man but he still has a bit on the side.

外遇-wài yù-Extramarital affair, a bit on the side (Noun)

Literal Translation-Outside encounter

这个老板和他的秘书有外遇。

zhègè lǎobǎn hé tāde mìshū yǒu wàiyù。

The boss had an affair with the secretary.

不忠- bù zhōng-Cheat (Adj)

Literal Translation-Not honest

我的丈夫对我不忠之后我就和他离婚了。

wǒde zhàngfu duì wǒ bù zhōng zhīhòu wǒ jiù hé tā líhūn le。

I divorced my husband after he cheated on me.

偷情-tōu qíng-Have a secret love affair (Verb)

Literal Translation-Steal passion

我的女朋友偷情被我发现了。

wǒde nǚpéngyǒu tōuqíng bèi wǒ fāxiàn le。

My girlfriend was having a secret love affair before I found out.

红杏出墙-hóng xìng chū qiáng-Be unfaithful to one's husband (Verb)

Literal Translation-Red apricot come out of wall

她红杏出墙的次数已经数不清了。

tā hóngxìngchūqiáng de cìshù yǐjīng shǔbùqīng le。

She was unfaithful to her husband more times than anyone can count.

负心汉-fù xīn hàn-Cheater (referring to a man) (Noun)

Literal Translation-Negative heart man

他是个负心汉，他已经因为外遇离过两次婚了。

tā shì gè fùxīnhàn，tā yǐjīng yīnwèi wàiyù lí guò liǎngcì hūn le。

He is a cheater. He has been divorced two times because of having extramarital affairs.

姘头-pīn tóu-Mistress (Noun)

Literal Translation-Cohabits head

他的姘头毁了他的婚姻。

tāde pīntóu huǐ le tā de hūnyīn。

Having a mistress ruined his marriage.

小老婆-xiǎo lǎo pó-Mistress (Noun)

Literal Translation-Small wife

我再也不想做你的小老婆了，我想做你真正的老婆。

wǒ zàiyě bù xiǎng zuò nǐde xiǎolǎopó le，wǒ xiǎng zuò nǐ zhēnzhèng de lǎopó。

I don’t want to be your mistress anymore. I want to be your real wife.

有一腿-yǒu yì tuǐ-Have an affair (Verb)

Literal Translation-Have one leg

她丈夫出差的时候她和她的同事有一腿。

tā zhàngfū chūchāi de shíhòu tā hé tāde tóngshì yǒuyìtuǐ。

She had an affair with her co-worker when her husband was on a business trip.

劈腿-pī tuǐ-Affair, cheat, two-timing (Verb)

Literal Translation-Split leg

你老婆有怀疑你劈腿吗？

nǐ lǎopó yǒu huáiyí nǐ pītuǐ ma？

Is your wife suspicious of you having an affair.

幽会-yōu huì-A secret meeting of lovers (Verb, Noun)

Literal Translation-Quiet meet

我们午饭的时候秘密幽会，谈论我们的未来。

wǒmén wǔfàn de shíhòu mìmì yōuhuì，tánlùn wǒmén de wèilái。

We had a secret meeting at lunch to have a conversation about our future.

二婚-èr hūn-The second marriage (Noun)

Literal Translation-Two marriage

那个情人被认为是他的二婚。

nàgè qíngrén bèi rènwéi shì tāde èrhūn。

The mistress was considered his “second marriage”.

戴绿帽子-dài lǜ mào zi-A cuckold, a man who is being cheated on. (Verb)

Literal Translation-Wear green hat

他被三个前妻带了绿帽子，她们都欺骗了他。

tā bèi sāngè qiánqī dài le lǜmàozǐ，tāmén dōu qīpiàn le tā。

He has been a cuckold by his last three wives. They all cheated on him.

脚踏两条船-jiǎo tà liǎng tiáo chuan-Have two lovers at the same time (Verb)

Literal Translation-Feet step on two boats

他已经脚踏两条船了还嫌不够。

tā yǐjīng jiǎotàliǎngtiáochuán le hái xián búgòu。

He has two girlfriends at the same time and he still wants more.