GNU Collaborative International Dictionary of English

Found one definition

1.       
   Mouthful (?), n.; pl. Mouthfuls ().
   1. As much as is usually put into the mouth at one time.
   
   [1913 Webster]
   
   
   2. Hence, a small quantity.
   
   [1913 Webster]
   
   
   3. A statement that has a profound truth in it; as, “you said a mouthful!” [informal]
   
   [PJC]