Write and send (someone) a note or telegram.(verb)
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Use "drop a line" in a sentence
"If you have, drop a line to Kevin Nelson, P. O. Box 1221, Benicia, California 94510."
"Last year when the roof started leaking — no, I'm a liar, it was two years ago now — all I had to do was drop a line and suggest it was a job too big for Willy here on his own and Mr Norbert wrote right back to say we should hire whoever we liked and send him the bills."
"- Carrie reminded me that as her old school friend, Annie Fullers (now Mr.. James), and her husband had come up from Sutton for a few days, it would look kind to take them to the theatre, and would I drop a line to Mr. Merton asking him for passes for four, either for the Italian Opera, Haymarket, Savoy, or Lyceum."