DM means Direct Message.
The Full Answer
DM is a slang abbreviation that stands for Direct Message.
DM functions are found on social media such as Instagram and Twitter, and on messaging apps such as Snapchat. A dm is a private message that can be sent to an individual person or a group conversation (often called a dm room).
Anything you don’t want to be made public, you can send via a dm. This could be…
flirting with someone…
or bitching about someone…
or saying something that others may find offensive.
It is considered bad etiquette to make public a dm you receive.
Often, the most meaningful messages are exchanged via dm instead of on public feeds, as you are less guarded and can be your true self. When this happens, you can say that it is down in the dm or it goes down in the dm.
Where Would You See DM?
In texting… and chat… and on social media such as Instagram… and Twitter… and Facebook… and messaging apps such as Snapchat.
Me when I get a dm from someone I don’t know.
Random DM Stuff
The slang term dm has its origins in the direct message feature on Twitter. Usage of the term really started to take off in 2008 as Twitter’s popularity soared.
Other social media, most notably Instagram and Snapchat, have since followed Twitter’s lead and use the term direct message on their apps to refer to a private exchange between users.
Other DM Meanings
Dungeon Master (in the role-playing game Dungeons & Dragons).
Deathmatch (a gameplay mode integrated into many video games).
Designated Marksman (a military marksman).
dm-drogerie markt (a German chain of retail stores).
Doctor of Medicine.
Deutsche Mark (official currency of Germany until 2002).
Decimeter (a unit of length).
Diabetes Mellitus (disease).
Defensive Midfielder (a position in soccer).