Collins Chinese Dictionary Plus (3rd edition), 2011:
彼此 bǐcǐ 代
1
(=双方) both sides
- 这(這)对(對)混双(雙)选(選)手彼此并(並)不太了解。 Zhè duì hùnshuāng xuǎnshǒu bǐcǐ bìng bù tài liǎojiě. This mixed-doubles pair don't know each other well.
2
(谦)
- "你这(這)次考得不错(錯)啊!""彼此彼此!" "Nǐ zhè cì kǎode bùcuò a!""Bǐcǐ bǐcǐ!" "You did really well in the exam!""You too!"
- "你看上去很棒啊!""彼此彼此!" "Nǐ kàn shàngqù hěn bàng a!""Bǐcǐ bǐcǐ!" "You look great!""Likewise!"