Clueless. Not with it. Out to lunch. Said of somebody who is uninformed about something. It comes from the 404 error message commonly found on the Web. See 404 error and offline.
Browse entries near 404
401(k) plan
401(k)'s
401K
403(b) plan
403(b) plan (investment)
404 error
4040
405LP
40V
40x CD-ROM
