The term 'Maximal DEGREE' is a mathematical concept which refers to the highest DEGREE of a polynomial. In mathematics, a polynomial is an expression consisting of variables and coefficients, that involves only the operations of addition, subtraction, multiplication, and non-negative integer exponents of variables. The NTH in this crossword solution stands for 'DEGREE', which is the highest power to which a variable is raised in a polynomial. Therefore, the answer to the crossword clue is 'NTH', which stands for 'Maximal DEGREE'.