When someone is "hanging on every word," it means they are paying close attention to what someone is saying. There are many synonyms for this expression that convey the same sentiment, such as "captivated," "spellbound," or "riveted." These words suggest not only close attention, but also a sense of emotional engagement with the information being shared. Similarly, phrases like "absorbed in," "enraptured by," or "entranced by" can also capture the sense of being fully invested in what someone is saying. Whether it's a captivating speaker or an important conversation, these expressions convey the idea of being completely focused and engaged.