noun
hand signals; flag signals
Refers to communication using hand gestures or flags, often in contexts like scouting, maritime, or military signaling. The term is somewhat specialized.
ボーイスカウトでは、てしんごを使って遠くの仲間と連絡を取る。
In Boy Scouts, they use hand signals to communicate with distant companions.
船の間でてしんごを送る。
They send flag signals between ships.
手話 is sign language used by deaf communities, whereas 手信語 refers to coded signals for communication over distance, not a full language.
Compound of 手 (hand) + 信 (signal/communication) + 語 (language/word). The exact origin is uncertain, but it appears to be a coined term for signaling systems.