Nailed down' is a phrase that is used to describe something that has been firmly established or secured. The crossword solutions for this term are 'pegged' (6 letters), 'ICED' (4 letters), 'secured' (7 letters), 'STATIONARY' (10 letters), and 'AUTHORITATIVE' (13 letters). Pegged can refer to something that has been fastened in place with a peg, while ICED implies that something has been frozen or cooled. Secured means that something has been made safe or protected, and STATIONARY suggests that something has been fixed in one place. Finally, AUTHORITATIVE implies that something has been established with authority or power.