means a dark outline or shape of someone or something shown filled in with solid color, usually black, against a lighter background.

from Named after Étienne de Silhouette, a French finance minister in the mid-18th century whose name became a byword for things done cheaply. The cut-paper profile portrait was the budget alternative to a painted one, so 'à la silhouette' came to mean done on the cheap — and the word stuck to the shadow-portrait itself, leaving the minister forever attached to the poor man's likeness.