the act of expanding or spreading out; the condition of being expanded; dilation; enlargement.-that which is expanded; expanse; extend surface; as, the expansion of a sheet or of a lake; the expansion was formed of metal.-space through which anything is expanded; also, pure space.-enlargement or extension of business transactions; esp., increase of the circulation of bank notes.-the developed result of an indicated operation; as, the expansion of (a + b)2 is a2 + 2ab + b2.-the operation of steam in a cylinder after its communication with the boiler has been cut off, by which it continues to exert pressure upon the moving piston.-the enlargement of the ship mathematically from a model or drawing to the full or building size, in the process of construction.