A mouthful is an amount of food or drink that fills your mouth in one bite or sip. When you take a mouthful of spaghetti, you're getting as much as you can comfortably chew at once. Your mom might tell you not to talk with a mouthful of food, meaning you should swallow before speaking.

The word also describes something difficult to say because it's long or complicated. Someone's full name might be “Alexander Maximilian Fitzgerald-Wellington III,” and people would call that quite a mouthful. Scientific terms like “photosynthesis” or tongue twisters like “she sells seashells” can be mouthfuls too. When you struggle to pronounce your friend's last name or the title of a book is ridiculously long, you might say “that's a mouthful!”

People sometimes use the phrase “say a mouthful” when someone makes a short statement that contains a lot of truth or meaning. If your friend says “math homework sure gets harder in sixth grade” and you reply “you said a mouthful,” you're agreeing that those few words captured something important.