Deep-seated ill will is a term used to describe a strong feeling of resentment or hostility that has been held for a long period of time. The two crossword solutions for this term are 'GRUDGE' and 'RANCOR'. A GRUDGE is a deep-seated feeling of resentment or ill will towards someone or something, while RANCOR is a feeling of deep-seated bitterness or hatred. Both terms are used to describe a long-standing negative emotion that has been held for a significant amount of time.