A DNS record
type as per RFC 2052
SRV in this context is short for service. Although still experimental, this type of record could turn out to be very useful, as it allows one to redirect queries for a particular service (i.e. http, ftp, irc, etc) to a specified host or even a seperate port.
The record itself is setup to be very versatile, allowing weightings, port redirection, and the target host. It's a shame that no current clients make use of this wondrous record type.