1. correspond; write a short letter or note
drop me a line/message
The idiom ‘to drop a line’ means to get in touch with someone or to correspond with them quickly or briefly. If you ‘drop a line’ it usually means to send a written note, email or message. If you ‘drop a message’ it can mean to correspond with someone briefly or to deliver a short message to them such as a note or verbal communication. Both are used in social and professional contexts.