1. Expand, dilate, distend, inflate imply becoming larger and filling more space. To expand is to spread out, usually in every direction: to expand one's chest. To dilate is especially to increase the width or circumference, and applies to space enclosed within confines or to hollow bodies: to dilate the pupils of the eyes. To distend is to stretch, often beyond the point of natural expansion: to distend an artery. To inflate is to blow out or swell a hollow body with air or gas: to inflate a balloon.

Did you mean expounding?