Gant is a build tool for scripting Ant tasks using Groovy instead of XML to specify the build logic. A Gant build specification is just a Groovy script and so can bring all the power of Groovy to bear directly, something not possible with Ant scripts. Whilst it might be seen as a competitor to Ant, Gant relies on all the Ant tasks for actually doing things, so it is really an alternative way of doing builds using Ant, but using a programming language rather than XML to specify the build rules.