A telegram—using electrical transmission to send short written messages over a distance. It was used widely in the past but has declined in modern use.
結婚式の知らせを親戚に電報で送った。
I sent news of the wedding to relatives by telegram.
昔の映画では重要な連絡を電報で伝える場面がよく出てくる。
In old movies there are often scenes where important messages are sent by telegram.