"extend the definition" is an acceptable phrase in written English.
It is typically used to signify that a definition is being made more specific or more inclusive. For example, you could say, "By extending the definition of financial success to include non-monetary rewards, one could include accomplishments such as earning a degree or learning a new skill."
A case in the works now, brought by goldminers against Anglo-American South Africa, may extend the definition of domicile.
But she was also careful to extend the definition of zero tolerance to include treatment and prevention programmes as well as crime and disorder crackdowns.
Part of Jazz Voice's remit is to extend the definition of "jazz" to include artists who had no idea they were jazzy.
If you extend the definition of "Fleet Street" to include neighbouring streets, all of us who work for the Euromoney group's publications in London are still here, including me.
Patrick Leahy's proposal to extend the definition of family to same-sex marriages was withdrawn, in deference to his fellow-Democrats, who pleaded that it would gut Republican support.
For instance, it would be reasonable to extend the definition of compulsory licensing to allow poor countries which, unlike Canada, lack the domestic industrial capacity to produce the drugs they need, to import them from elsewhere.
Cliff Stevenson, an anti-dumping consultant who has worked for the commission, says that one option could be to extend the definition of community industry to include European businesses with overseas operations.
We also extend the definition of the Chern character to include certain unbounded operators.
Hence, we propose to extend the definition of SASs and include context adaptation.
Now we want to extend the definition of well-formed processes to sets of places.
Now, we redefine and extend the definition of Morrey norms adapted to the function Φ.
