The term 'BIG PAIN' can be broken down into two crossword solutions: HEADACHE (8 letters) and AGONY (5 letters). HEADACHE is a common medical condition that is characterized by a throbbing or pulsing sensation in the head, often accompanied by nausea, vomiting, and sensitivity to light and sound. AGONY is an intense physical or mental suffering, typically caused by distress, affliction, or grief. Both of these terms are used to describe a large amount of pain or suffering.