The term 'conservative opening' in chess refers to a type of opening move that is designed to be safe and solid, rather than aggressive. The two crossword solutions for this term are NEO (3 letters) and ULTRA (5 letters). NEO is an abbreviation of the Latin phrase 'nihil novi, ' which translates to 'nothing new, ' and is often used to describe a conservative approach to something. ULTRA is a Latin prefix meaning 'BEYOND, ' and is often used to describe something that is more extreme or intense than usual. Therefore, NEO and ULTRA can both be used to describe a conservative opening in chess.