verb (v)

• bite or chew on with the teeth(verb.contact)

  Example:
  Gnaw an old cracker.
  

  source: wordnet30
• become ground down or deteriorate(verb.change)

  Synonym:
  eat at, erode, gnaw at, wear away
  

  source: wordnet30
• To bite, as something hard or tough, which is not readily separated or crushed; to bite off little by little, with effort; to wear or eat away by scraping or continuous biting with the teeth; to nibble at.(verb)

  source: webster1913
• To use the teeth in biting; to bite with repeated effort, as in eating or removing with the teethsomething hard, unwiedly, or unmanageable.(verb)

  source: webster1913