U
u-
UBD
UBE
ubergeek
UCE
UDP
UN*X
undefined external
reference
under the hood
undocumented feature
uninteresting
Unix
Unix brain damage
Unix conspiracy
Unix weenie
unixism
unswizzle
unwind the stack
unwind-protect
up
upload
upstream
upthread
uptime
urchin
URL
Usenet
Usenet Death Penalty
user
user-friendly
user-obsequious
userland
Utah teapot, the
UTSL
UUOC