sēmainō

This verb belongs to the family of the Greek noun for a sign (σημεῖον). Where one Greek word simply hands over information and another makes a thing clear, this one gives a pointer: the speaker puts up a marker, and the hearer has to follow it to reach the thing itself. In older Greek it was the standard word for what an oracle does, showing without saying.

Three of its six appearances are John's own aside about something Jesus had just said. Jesus speaks of being lifted up, or tells Peter where he will one day be led, and the narrator steps in to explain that the saying was a pointer to the kind of death that was coming (John 12:33, John 18:32, John 21:19). The word fits exactly, because the saying and the death only line up once the death happens.

The other three uses spread across the range:

• a prophet in Antioch announces a famine that is on its way (Acts 11:28)
• a Roman governor complains that he cannot send a prisoner to Caesar without stating the charges (Acts 25:27)
• the opening line of Revelation says God signaled to John what must soon take place (Revelation 1:1)

So one verb covers a hint whose meaning waits on events, a warning about the near future, and a plain administrative note. What holds them together is not how veiled the message is, but the act of pointing: someone puts up a sign, and someone else has to read it.