備胎bèitāi：It means spare tire originally, here it refers to rebound guy or girl.
例句：
1上(shàng)個(gè)月(yuè)，我(wǒ)的(de)女(nǚ)朋(péng)友(yǒu)和(hé)她(tā)前(qián)男(nán)友(yǒu)結(jié)婚(hūn)了(le)，原(yuán)來(lái)我(wǒ)是(shì)當(dāng)了(le)兩(liǎng)年(nián)的(de)備(bèi)胎(tāi)。
Last month, my girlfriend married her ex-boyfriend. It turned out I had been a rebound guy for two years.
2.你(nǐ)明(míng)明(míng)知(zhī)道(dào)她(tā)不(bù)愛(ài)你(nǐ)，還(hái)對(duì)她(tā )那(nà)麼(me)好(hǎo)，你(nǐ)是(shì)心(xīn)甘(gān)情(qíng)願(yuàn)當(dāng)備(bèi)胎(tāi) ？
You obviously know she doesn’t love you, but you still do too many things for her, are you so willing to be her rebound guy?
3. A:給(gěi)我(wǒ)介紹(jièshào)個(gè)女朋友(nǚpéngyǒu)吧(ba)!
Introduce me a girlfriend!
B:麗(lì)麗(lì)不是(búshì)你(nǐ)的(de)女朋友(nǚpéngyǒu)嗎(ma)？
Isn’t lili your girlfriend?
A:我(wǒ)並不(bìngbù)愛(ài)她(tā)，她(tā)只(zhǐ)是(shì)一(yī)個(gè)備(bèi)胎(tāi)。
I don’t really love her, she is just my rebound girl.
