sfu·ma·to 
(sf-mätō)
(sf-mätō)n.
The blurring or softening of sharp outlines in painting by subtle and gradual blending of one tone into another.
[Italian, from past participle of sfumare, to evaporate, fade out : s-, from (from Latin ex-; see EX-) + fumare, to smoke (from Latin fūmāre; see FUMATORY).]