A fogy is an old fashioned, boring, unstylish person. You might accuse your dad of being an old fogy if he tells you to turn down your music.
You can spell the word fogy or fogey — either way, you're probably talking about an older person, and you're definitely talking about a dull, conservative person. The word comes from the Scottish foggie, and it originally meant "an army veteran." Fogy may be related to the antiquated slang word fogram, "old fashioned person," or from an early, now obscure meaning of fog, "bloated fat."