1. Having large round wide-open eyes, often expressing surprise or fear
   "The child was round-eyed at the sight of the enormous Christmas tree";
   - saucer-eyed
    
2. Exhibiting childlike simplicity and credulity
   "listened in round-eyed wonder";
   - childlike, wide-eyed, dewy-eyed, simple

See also: eyed, naif, naïf, naive, naïve