vhost

a "vhost" is either a vanity host, or a virtual host.
on a place like IRC, vhost usually refers to a vanity host.
vanity hosts are domains that usually make up some sort of sentence, such as:
did.time.for.illegal-warez.net
these kind of hosts show up when a person on IRC searches for your username.
usually, one would have some kind of generic host provided by your ISP, or possibly your actual IP if the IRC server you're on fails to do a reverse dns on your IP.

most shell services provide options to include vhosts like this, since most either control an uplink or host a dns server, or both.

those who create such vhosts often use domain suffixes (such as .com, .net, and .org, but more commonly more obscure ones such as country suffixes and stuff like .name) as part of the actual made by the domain, such as:

uses.a.fake.host.name

a list of country TLD's, or top level domains (domain suffixes) can be found at:
ana.org/cctld/cctld-whois.htm

Now that i'm writing this definition, the word virtual host reminds me of a feature just about every commercial webhosting company provides, which i believe is the ability to host more than one website on the server.