means A detectable sign, gesture, or transmitted impulse that conveys information or prompts an action, especially across distance or through a noisy medium.

from From Latin 'signum' (a mark, token, sign) — the same root that gives us 'sign' and 'signature.' Through Medieval Latin 'signale' (a sign agreed upon) it slipped into Old French and then English, first as something you flash or wave to convey meaning, later swelling to cover the electrical and radio pulses that now carry the universe's gossip for us.