impetigo Syllabification: (im·pe·ti·go)Pronunciation: /ˌimpiˈtīgō, -tē-/Definition of impetigo noun a contagious bacterial skin infection forming pustules and yellow, crusty sores. This disease is caused by the bacteria Streptococcus pyogenes or S. aureus Origin: late Middle English: from Latin, from impetere 'to assail, attack'impetigo in other Oxford dictionaries Definition of impetigo in the British & World English dictionary