measure word, noun · a unit of time equal to one-sixtieth of a minute

现在是三点十分二十秒。

verb, measure word · immediately or in an instant, often used in internet slang

他秒回了我的微信。

measure word · a unit of angular measurement equal to one-sixtieth of an arc minute

这个角度的误差仅为几秒。

measure word · (slang) to finish a task or defeat an opponent in an instant; often used in the context of online shopping (to snatch up items) or gaming

这款手机太抢手了，刚上架就被秒了。