The term 'SOLUTION STRENGTH' can be defined by two crossword solutions, 'Titer' and 'Titre'. Titer is a term used in laboratory testing to measure the concentration of a solution. It is usually expressed as a ratio or fraction, and is determined by comparing the amount of a substance in a solution to a standard amount. Titre is a French term that is used to describe the same concept as titer. Both terms are used to measure the strength of a solution.