Toughness is a quality that can be described in many ways. FIRMNESS, with 8 letters, is the ability to remain strong and unyielding in the face of difficulty. Hardiness, with 9 letters, is the capacity to withstand difficult conditions or situations. SINEW, with 5 letters, is strength and resilience of muscle and tissue. GRIT, with 4 letters, is courage and resolve in the face of adversity. STEEL, with 5 letters, is a metaphor for strength and durability. GUTS, with 4 letters, is another metaphor for courage and determination. Finally, RIGOR, with 5 letters, is the quality of being extremely thorough and exacting. All of these words describe the quality of toughness.