Best in slot (usually shortened to "BiS") is a term meant to describe the very best item, enchant and/or gem available to a character for a specific slot. While there are differences in opinion there is usually a generally held idea of what is the BiS. This term is used by the twink community for things that are best for particular levels, while it usually refers to level cap things.

Some players consider such "BiS lists" to be absolute, while others consider best in slot to be relative to your other gear, talent specialization, and play style.