From Pluralpedia, the collaborative plurality dictionary
crosstalk (n., v.)
Other formscrosstalking

Crosstalk refers to headmates from the same system using a form of written or typed communication in the outerworld to talk to each other.

Examples of ways that headmates can crosstalk include typing in a Discord server to each other, writing notes on paper for each other, tapping letters on a sign to spell words to each other, pointing to words in a book to speak to each other, and other methods not listed here.

While some forms of crosstalk are instant, communication does not have to be instant to be considered crosstalk. Similarly, while many instances of crosstalk involve a headmate writing or otherwise communicating themself, a headmate speaking to another headmate through thoughtsharing and then having the second headmate write it down is also considered crosstalk. Conversations do not have to be solely written, typed, or tapped to be considered crosstalk conversations.