wtf is a small package optionally distributed with the cygwin environment. Presumably, a real *nix version must exist somewhere, but I haven't been able to find it.

The goal of the wtf tool is to help you navigate the sea of acronyms on the Internet. The command-line syntax is: wtf [is] <acronym|extension>

This package is marginally useful, but lacks sufficient documentation and coverage to make it usable. So, it knows about jpeg but not about jpg or ASCII. Moreover, it does not have the nicely professional finished feel that most Cygwin (and unix in general) utilities do: If no match is found, it doesn't print anything (an error message would be more helpful). The database of acronyms is very small (e.g., it doesn't recognize irc), though you can add your own if you have the devotion.

The BUGS section of the man page says it all: it's an unfinished program that was included in Cygwin for no clear reason:

     The index files are not transportable across machines of different
     endian-ness and/or with different sizes of unsigned long.

     The command-line argument handling code is very rudimentary.

     No doubt there are a great many more. If you find any, please squash them
     and send the pieces to the author.

Edit: I have been informed that this is an old BSD package which first appeared in NetBSD 1.5. So I guess the reason I've only ever found it in Cygwin is that the school computers and our family server are all Fedora Red Hat stuff.
Swap tells me that the Debian version is actually better. Maybe it's just the Cygwin port that's not very polished.