alt Hacker NewsOther than what the others mentioned about finding more efficient representations, you can also compress by pre-agreeing on some common terminology.
In many ways, we are communicating using a compressed channel (words) since we both have pre-agreed on the meaning of these words.
That and also that agreements can evolve with time and also within a discussion, so a basic level of agreement is necessary, but complete consensus about the meaning of all words is unnecessary and often unproductive to communications held in good faith.