The term 'MOST SECURE' can be defined by two crossword solutions: SAFEST (6 letters) and FASTEST (7 letters). SAFEST is an adjective that means the most protected from danger or harm, while FASTEST is an adjective that means the quickest or most rapid. Both words are used to describe something that is secure, but in different ways. SAFEST implies that the object is well-protected from any potential threats, while FASTEST implies that the object is able to respond quickly to any potential threats.