The term 'give a piece of one's mind' is an idiom that means to express one's opinion or feelings in a strong and forceful manner. The two crossword solutions for this term are OPINE (5 letters) and LACEINTO (8 letters). OPINE is a verb meaning to express an opinion, while LACEINTO is a verb meaning to express one's opinion forcefully. Therefore, both words can be used to describe the same action of expressing one's opinion in a strong and forceful way.