In wireless (specifically ["802.11b"]) an ad-hoc network is where all the wireless clients talk directly to each other. This is as opposed to BssMode (or InfrustructureMode) where clients talk to each other via an AccessPoint.
[http://www.goonda.org/wireless/prism2/ This] is an excellent page regarding ["Prism2Card"]s, their firmware issues, wvlan_cs, and IBSS mode. --AndrewWoods