The term 'make thinner' can be solved in a crossword puzzle using the words DILUTE (6 letters), EMACIATE (8 letters), and RAREFY (6 letters). DILUTE means to reduce the strength or concentration of a substance by adding another substance. EMACIATE means to make extremely thin and weak, usually due to illness or starvation. RAREFY means to make less dense or more scattered. All three words refer to making something thinner, either in terms of concentration, physical size, or density.