The phrase "give an earful" means to express one's opinion strongly and at length. Synonyms for this expression include "rant," "vent," "harangue," "chew out," "lecture," "rebuke," "berate," and "scold." Each of these phrases connotes a strong and forceful delivery of one's thoughts and feelings. Additionally, some less harsh synonyms for "give an earful" include "explain," "debate," "discuss," and "give feedback." These phrases imply a more balanced and measured approach to expressing one's opinion. Regardless of the synonym used, the sentiment remains the same: the speaker has a strong opinion and wants to be heard.