1) the underside of an arch, architrave, ceiling, beam, or other similar structure
http://dictionary.reference.com/search?q=soffit
architrave -
1) lowermost horizontal component of a classical (Greek, Roman) building, resting upon a column
2) molding on top of a door
Another architrave.
http://dictionary.reference.com/search?r=2&q=architrave
Obscure word of the day April 8, 2008