noun
(uncommon) Synonym of telegraphy, any process for transmitting arbitrarily long messages over a long distance using a symbolic code.
(chiefly historical) The electrical device gradually developed in the early 19th century to transmit messages (telegrams) using Morse code; the entire system used to transmit its messages including overhead lines and transoceanic cables.
(video games) A visible or audible cue that indicates to an opponent the action that a character is about to take.
verb
To use a telegraph, send a message by telegraph.
(figurative) To clearly communicate to another nonverbally, whether by gesture, a change in attitude, or any other sign, especially unintentionally.