Now that spring is here, we turned back on the water supply for the outdoor spigots. Water started flowing normally out of the spigot attached to the outside of the back of our house but when we went to turn off the water (using the knob on the spigot), the knob wouldn't budge. We have tried loosening it with pliers and by spraying WD-40 on it and it still won't budge. Aside from hiring a plumber to come out and replace the entire spigot, is there something else I could try to loosen it?

HI,
Did you try tapping it gently with a wrench, hammer, or other hard object?
After the WD-40 has time to run down into it, it might come loose with a gently tap; not hard though.