Silhouette
The Basic Concept
Silhouette is the shape of an object, thus it is used in fashion to describe the shape of a person and the shape of clothing ON that person. For example, a thin male with slim-fitting clothing would have a slim silhouette, while one with relaxed, baggy clothing would have a baggy silhouette. Some designers are known for pushing very slim silhouttes (Hedi Slimane for example) and other for pushing a loose, baggier silhouette (Yohji Yamamoto for example. No silhouette is inherently better or worse.
Examples
Dropcrotch vs Normal Crotch
The image on the right shows the difference between the silhouettes of dropcrotch and normal sweatpants.
Small vs Large Toeboxes
The image on the left shows the difference between large and small toeboxes. Red Wing Mocs are notorious for their large toeboxes, which tend to cause shoes to be called "clown shoes", because of the large toeboxes of clown shoes. The image below demonstates the difference between large and small toeboxes.
External Links
https://en.wikipedia.org/wiki/Silhouette#Fashion_and_fitness
http://www.fashion-era.com/C20th_costume_history/1940s-silhouettes-dresses-1940-1949.htm