The term CALC COUSIN is a combination of two words, 'calc' and 'COUSIN'. Calc is short for 'CALCULATOR', which is a device used to perform mathematical calculations. TRIG is the four-letter word that is the crossword solution for this term, and it stands for trigonometry, which is a branch of mathematics that deals with the relationships between angles and sides of triangles. Trigonometry is closely related to calculus, which is why it is referred to as the 'COUSIN' of calculus.