The term 'on the double' is an idiom that means to do something quickly or immediately. It is often used in job descriptions to indicate that a task needs to be done as soon as possible. The crossword solutions for this term include STAT (4 letters), CHOP (4 letters), NOW (3 letters), PDQ (3 letters), ASAP (4 letters), FAST (4 letters), APACE (5 letters), ATONCE (6 letters), PRESTO (6 letters), PRONTO (6 letters), SWIFTLY (7 letters), CHOPCHOP (8 letters), INAFLASH (8 letters), CHOPECHOED (10 letters), and LICKETYSPLIT (12 letters). All of these words are synonyms for the phrase 'on the double' and indicate that a task should be done quickly or immediately.