NOUN (2)

1. a headscarf worn by Muslim women; conceals the hair and neck and usually has a face veil that covers the face;

2. the custom in some Islamic societies of women dressing modestly outside the home;
- Example: "she observes the hijab and does not wear tight clothing"

WordNet (r) 3.0 (2006):

hijab
    n 1: a headscarf worn by Muslim women; conceals the hair and
         neck and usually has a face veil that covers the face
    2: the custom in some Islamic societies of women dressing
       modestly outside the home; "she observes the hijab and does
       not wear tight clothing"