约会 (yuēhuì) means "a date" or "an appointment," most commonly referring to a romantic outing between two people. It can be used as both a noun and a verb, as in 去约会 (go on a date) or 一个约会 (a date).
今天晚上我和男朋友有个约会。
jīntiān wǎnshang wǒ hé nánpéngyou yǒu gè yuēhuì.
I have a date with my boyfriend tonight.
他们第一次约会是在一家咖啡馆。
tāmen dì yī cì yuēhuì shì zài yī jiā kāfēiguǎn.
Their first date was at a café.
周末我要去约会,就不陪你逛街了。
zhōumò wǒ yào qù yuēhuì, jiù bù péi nǐ guàngjiē le.
I'm going on a date this weekend, so I won't go shopping with you.