n. The act of expanding.n. The act of extending or distending, or of increasing in extent, size, bulk, amount, etc.n. The state of being expanded; enlargement; distention; dilatation; increase of extent, size, bulk, amount, etc.n. Specifically The increase in bulk of steam in the cylinder of an engine when its communication with the boiler is cut off, in which case its pressure on the piston retreating before it is in inverse ratio to the space it fills.n. A part which constitutes an increase or in which the expanding occurs; specifically, in entomology, a flat projection of a margin, generally lateral: as, a frontal expansion covering the base of the antennæ.n. Extension or spread of space; extent in general; hence, wide extent; immensity.n. In mathematics, the development at length of an expression indicated in a contracted form, especially by means of the distributive principle.n. In ship-building, a drawing in which a curved or warped surface, as a ship's outside plating or a longitudinal, is laid out or expanded on a plane surface by conventional methods to show approximately the true relations and dimensions of the parts.