Hose Bib won't turn off (only spins)

Gentlemen (and women),
I have a plumbing question for you. First of all my house is built in 1975 in Northeast Kansas (Kansas City metro area).

My roommate went to wash his vehicle today and I, later, went to run the hose, which he left on (there was a sprayer-handle on-off on the end of the hose, preventing the water from running). When I went to shut it off (via hose bib), all it does is spin and spin, not sealing to shut off the water.

This seems like it would be a common problem, but I could not find anything in the forum except for "leaky hose bib" and "leaky backflow hose bib" issues.

The hose bib does not appear to be a backflow prevention or frost proof model (I believe it to be original to the house circa 1975). I have done minor plumbing work including replacing the neoprene washer seal on the main coming into the house, but am VERY unfamiliar to the vocabulary associated with the specific parts of a hose bib, so you'll have to be patient with me in that aspect.

Thank you all in advance for taking the time to read this.

-Matt

Old gate valve type of bib or boiler bib. Need to find out if there is a shutoff inline somewhere supplying the hose bib.

It's definitely a boiler-style bib as shown here on the left:
http://www.allproducts.com/metal/goodyear/19-brass_cxc_male_boiler-723-l.jpg

Why would an inline shutoff make any difference? I'm trying to get it to turn OFF, not ON, which would nulify any inline shutoff to the hose bib, correct?

The handle is stripped take the handle off turn the stem with pliers to off.

faucet

The stem is most likely stripped and unless you can find a valve exactly like it and use its parts for the repair, you have to replace the faucet.