Copy

On the CB, 'copy' means the message came through and you got it. Acknowledgment, plain and simple. Borrowed straight from military and amateur radio, where 'copy' has always meant successfully receiving a transmission. Truckers shortened the whole exchange into one word — say 'copy' and the other driver knows you're tracking.

As a question — 'copy?' or 'do you copy?' — it's a check-in. Did you hear me, are we still connected, are you actually paying attention. Standard radio etiquette dragged into everyday speech, especially anywhere people work with headsets or radios.