Meaning is not carried by the words, it’s carried by your mind. We assume that we assign the same meanings, but that’s a big assumption.
These online conversations, composed of words and only words, are arguably 99% us just talking to ourselves. Maybe even 100%.
You could stand next to the guy while you both look at the relevant thing. That’s a pretty good way.
Another way would be to use the same method for looking at the relevant thing. Let’s call it “an experimental method”. Because it delivers an experience.
What does water taste like?
Get a glass of water and taste it. It tastes like that.
But how would I know if our experience of the taste of water is the same?
Because it’s water.
You’d have to settle for close enough here. You might even drink from the same glass. Beyond that … until we invent telepathy.