DM       
 noun [ C ]  internet & telecoms informal uk/ˌdiːˈem/ us/ˌdiːˈem/
 (在社交网站上发送的)私信(direct message 的缩写)
abbreviation for direct message: a private message sent on a social media website, that only the person it is sent to can see
  She received threats and abuse in her DMs. 她在私信中受到威胁辱骂。 
 DM       
verb [ I or T ]  internet & telecoms informal uk/ˌdiːˈem/ /ˌdiːˈem/
 (在社交网站上)发私信,收发直接信息(direct message 的缩写)
abbreviation for direct message: to send someone a private message on a social media website
  I'm selling my bike. DM me if you're interested. 我有一辆自行车出售,有兴趣的话可以给我发私信。