Definitions of nibble:

• noun:   gentle biting
• noun:   a small byte
• verb:   eat intermittently; take small bites of

  Example: "She never eats a full meal--she just nibbles"

• verb:   bite gently

  Example: "The woman tenderly nibbled at her baby's ear"

• verb:   bite off very small pieces

  Example: "She nibbled on her cracker"