*NIX and *BSD program standing for "Secure SHell" which has many different commercial implementations along with an open-source implementation called OpenSSH.
It is used to remotely login to a computer running SSHDSecure SHell Daemon using a username a password and then execute commands on the remote machine. Works nicely when you have your parents running Gentoo Linux like I do. =^_-=
It is also the abreviation for the japanese metal band Saitama Saishuu Heiki, which makes arrangements of videogame music and some original compositions.
Skank slut hoe. SSH is to be used in times when you need more than one word to describe how slutty a person is because sometimes only using the word skank doesn't always say enough.