A workstation... without any disks!
Normally implies some sort of network booting (PXE, TFTP etc) to get the boot image, then booting and mounting a FileSystem over a network.
A ThinClient is a class of DisklessWorkstation, but instead of having a local filesystem, it tends to log straight into a TerminalServer.
See DisklessWorkstationNotes for the lowdown.
2 pages link to DisklessWorkstation: