Noun

The act or process of expanding.

The expansion of metals and plastics in response to heat is well understood.

The fractional change in unit length per unit length per unit temperature change.

A new addition.

My new office is in the expansion behind the main building.

A product to be used with a previous product.

This expansion requires the original game board.

That which is expanded; expanse; extended surface.

* Beattie

the starred expansion of the skies

(steam engines) 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.

Noun

(en noun)

A violent release of energy (sometimes mechanical, nuclear, or chemical.)

* {{quote-magazine, date=2013-06-21, author= Chico Harlan

, volume=189, issue=2, page=30, magazine=(The Guardian Weekly) , title= Japan pockets the subsidy … , passage=Across Japan, technology companies and private investors are racing to install devices that until recently they had little interest in: solar panels. Massive solar parks are popping up as part of a rapid build-up that one developer likened to an "explosion ."}}

A bursting due to pressure.

The sound of an explosion.

A sudden uncontrolled increase.

*

As with the Lejeuneaceae, this pattern of massive speciation appears to be correlated with the Cretaceous explosion of the angiosperms and the simultaneous creation of a host of new microenvironments, differing in humidity, light intensity, texture, etc.

A sudden outburst.

* {{quote-magazine, date=2013-08-10, volume=408, issue=8848, magazine=(The Economist)

, title= Can China clean up fast enough? , passage=All this has led to an explosion of protest across China, including among a middle class that has discovered nimbyism. That worries the government, which fears that environmental activism could become the foundation for more general political opposition. It is therefore dealing with pollution in two ways—suppression and mitigation.}}