Yup, frigorific really is a word. It means “causing or producing cold”.
An article from World Wide Words reports that “the most common appearance of frigorific is in that characteristically American phenomenon, the spelling bee.” Aside from that, this rare word is usually reserved for scientific jargon; for example, Wikipedia has an entry about frigorific mixtures, combinations of “chemicals that achieve an equilibrium temperature independent of the temperature that the two chemicals started at.”
But when I see the word, I keep thinking it says fridge-orific. Sounds more like a cheesy exclamation about how terrific a refrigerator is. By the way, the words frigorific and refrigerator both come from the Latin root frigus, meaning (yes, you guessed it!) cold.