Drop a line.
Send a message or call.
To "Drop a line" means to send a brief message or make a quick phone call. It’s a friendly, informal way of encouraging someone to keep in contact, typically suggesting that the person write a note, an email, or make a short call.
Example Sentences
Don't forget to drop a line when you get to London!
The speaker is reminding someone to send a message when they arrive in London.
Just wanted to drop a line and say hi!
The speaker is sending a quick message to say hi.
If you have time, drop a line; we haven't heard from you in ages!
The speaker asks someone to get in touch because they haven't heard from them in a long time.
