Meaning:
“逆行” means “to go against the trend,” and “者” refers to “a person.” The title of the theme song of the 2019 Chinese movie “The Bravest,” which tells a moving story of the firefighters, this term has been used frequently to refer to medical professionals who work hard to combat the COVID outbreak and save lives. As the common folks are trying to stay away from the crowd during this period, doctors keep working in risky environments. The image is to overcome difficulties and shoulder more responsibility in times of danger.
Example:
A: 你姐姐是医生，这段时间很忙吧？
Nǐ jiějiě shì yīshēng，zhèduàn shíjiān hěn máng ba？
A physician, your elder sister must be very busy these days.
B: 是啊，她是肿瘤科医生，因为人手不够也去发热门诊值班了。
Shì a，tā shì zhǒngliúkē yīshēng，yīnwèi rénshǒu búgòu yě qù fārè ménzhěn zhíbān le。
Indeed. She is an oncologist, but has to work at the fever clinic which is lack of hands now.
A: 多亏有他们这些逆行者，疫情才得以控制。
Duōkuī yǒu tāmen zhèxiē nìxíngzhě，yìqíng cái déyǐ kòngzhì。
Thanks to brave people like her, the outbreak is under control.