An account on a unix-like operating system which grants the user access to a command line interface called a shell. Back in the day, this was the premiere service that ISPs offered because once one owned a shell account, he or she could access internet based services like IRC, email, USENET and other items that are now associated with PPP and GUIs. One can still procure shell accounts from most ISPs (the small ones, most national ISPs will not offer this type of service due to the additional costs and maintenance) however it is much more common to simply setup a Linux box and use your own. Some people run boxes and offer shell accounts to friends with narrower bandwidth or with a lack of technical proficiency.