Toughen is a term that can be used to describe the process of making something stronger or more resilient. The crossword solutions for this term include STEEL (5 letters), STRENGTHEN (10 letters), ACCLIMATE (9 letters), TEMPER (6 letters), HARDEN (6 letters), ENURE (5 letters), ANNEAL (6 letters), INURE (5 letters), and ADAPT (5 letters). STEEL is an alloy of iron and carbon, and is often used to make objects stronger and more durable. STRENGTHEN is a verb meaning to make something stronger or more resilient. ACCLIMATE is a verb meaning to ADAPT to a new environment or situation. TEMPER is a verb meaning to make something less extreme or intense. HARDEN is a verb meaning to make something harder or more resistant. ENURE is a verb meaning to become accustomed to something. ANNEAL is a verb meaning to heat and then cool a material in order to make it stronger and more durable. INURE is a verb meaning to become accustomed to something unpleasant. ADAPT is a verb meaning to adjust to a new environment or situation. All of these words can be used to describe the process of toughening something.