"Software that integrates work on a single project by several concurrent users at separated workstations."

There are two common definitions for this:

MicrosoftCorporation's Definition
Shared calendaring. Better referred to as a shared PersonalInformationManager, really.
Lotus's Definition
Shared information management with databases and forms and all the stuff that a group of people might want to work on.

Some examples of GroupWare include MicrosoftExchange, LotusNotes?, and Zimbra.