The term 'not allow' can be expressed in a variety of ways, as demonstrated by the crossword solutions given. The three-letter solutions are 'BAR, ' 'BAN, ' and 'NIX, ' which all mean to prevent or prohibit something. The six-letter solution, 'OUTLAW, ' means to make something illegal. The four-letter solutions, 'DENY' and 'VETO, ' both mean to reject or refuse something. The nine-letter solutions, 'BARRICADE, ' 'BLACKLIST, ' and 'INTERCEPT, ' all involve blocking or preventing something from happening. All of these words can be used to express the idea of not allowing something.