The term 'ne plus ultra' is a Latin phrase meaning 'nothing further beyond'. It is often used to refer to something that is the best or most perfect example of its kind. The crossword solutions for this term are EXTREMITY (9 letters), EPITOME (7 letters), IDEAL (5 letters), APEX (4 letters), ACME (4 letters), and ULTIMATE (8 letters). All of these words can be used to describe something that is the highest or most perfect example of its kind, and they all relate to the idea of 'ne plus ultra'.