Interior angle (Geom.), an angle formed between two sides, within any rectilinear figure, as a polygon, or between two parallel lines by these lines and another intersecting them; -- called also internal angle. -- Interior planets (Astron.), those planets within the orbit of the earth. -- Interior screw, a screw cut on an interior surface, as in a nut; a female screw.

Syn. -- Internal; inside; inner; inland; inward.

Department of the Interior, that department of the government of the United States which has charge of pensions, patents, public lands and surveys, the Indians, education, etc.; that department of the government of a country which is specially charged with the internal affairs of that country; the home department. -- Secretary of the Interior, the cabinet officer who, in the United States, is at the head of the Department of the Interior.