The term 'Number Two' is often used to refer to someone who is second in command. This can be seen in the crossword solutions provided, which include 'DEPUTY' (6 letters), 'VICE' (4 letters), 'Veep' (4 letters), and 'AIDE' (4 letters). The word 'Poo' (3 letters) is also a possible solution, although it is not as commonly used. All of these words refer to someone who is subordinate to another person or group.