$BTC

When it is said “listing with BTC pair”, it means:

Listing a new cryptocurrency for trading against Bitcoin (BTC).

For example: if the currency XYZ/BTC is listed, users can trade currency XYZ for BTC.

It may mean opening a trading position or announcing a trading strategy focused on the BTC pair against another currency:

Such as: ETH/BTC, ADA/BTC, or any other pair where the second currency is priced in BTC.

“Listing with BTC pair” may be part of a promotional or advertising campaign:

Such as a project announcing the listing of its currency for trading with BTC as part of its expansion.