Outline, contour, profile, skyline, silhouette mean the boundary lines which give form or shape to a body, a mass, or a figure.
Outline refers to a line which marks or seems to mark the outer edge or limits of a thing.
Contour does not fix the attention on an edge or limit but on the outer lines, particularly the curving lines, of a thing's shape as indicative of its grace or lack of grace, its fullness or slenderness, its softness or harshness.
Specifically, contour applies to lines (contour lines ) in a map (contour map ) that indicate the details of elevation of a country or tract of land.
Profile applies primarily to the representation or the appearance of something in outline, especially of a face in side view showing the contour of the head and emphasizing the line from forehead to under the chin.
Consequently, profile is often preferred when a varied and sharply defined outline as seen against a background is implied, although skyline may be chosen as more specific when the background is the sky.
Silhouette in its primary sense applies to a likeness of someone or something made by or as if by tracing the outline of his or its shadow on dark material (as black paper), cutting this out, and mounting it against a contrasting background. In extended use silhouette, even more than outline or profile, eliminates all consideration of such details as color, quality, and expression and implies an outline seen in or as if in a shadow.