черкнуть строчку; написать пару слов(о письме, открытке • "Well, and if you have a time, please drop me a line". == "И если у тебя будет время, обязательно напиши мне".)
черкнуть словечко(The crystal ship is being filled A thousand girls, a thousand thrills A million ways to spend your time when we get back I'll drop a line. (The Doors))
дать знать(особ. что все благополучно; let someone know how you are going, either by texting or calling • Please drop me a line when you get to Paris; I'd like to know that you've arrived safely. • I'll drop you a line when I get to the airport (= I'll give you a call). • I'll drop you a line as soon as I hear back from Richard.4uzhoj); сообщить(either by texting or calling; дать знать • I'll drop you a line as soon as I hear back from Richard.4uzhoj); отписаться(что все благополучно 4uzhoj); отзвониться(что все благополучно • I'll drop you a line when I get to the airport (= I'll give you a call) 4uzhoj)
протелеграфировать(Make sure you drop me a line when you get to the airport. • Just drop me a line when you land here and we can meet up for some lanes.Interex)
thefreedictionary.com • I'll drop you a line once I get settled in at school.)