Hairy means covered in a lot of hair. A hairy chest, a hairy dog, hairy legs.
It also describes anything with a rough fibrous surface: hairy stems, hairy fabric. The informal sense is frightening or dangerous — a hairy moment, the drive was a bit hairy — which is very common in British speech and has nothing to do with hair at all. Note hair-raising, which means the same thing more literally, and that hairy is one of the few adjectives that is both plainly descriptive and comically loaded.
1adjectivehairyCovered in a lot of hair.
“The dog is hairy and the whole house knows it.”
2adjectivefrighteningFrightening or dangerous.
“The last mile of that road is a bit hairy in the wet.”
hairy is a quality of hairiness or danger.
Also accepted in games: furry
Hairy is hair plus -y, from Old English haer. The frightening sense is twentieth-century and probably from the idea of hair standing on end, which is what the same fear does in hair-raising.
Middle English
hery
English, today
hairy
From Middle English hery, heeri, hary, equivalent to hair + y. Compare stq hierich (“hairy”), West Frisian hierrich (“hairy”), Dutch harig (“hairy”), German Low German harig (“hairy”), German haarig (“hairy”), Swedish hårig (“hairy”), Icelandic hárugur (“hairy”). Compare also Old English hǣriht (“hairy”) and ġehǣre (“hairy”). The sense "terrifying, scary" possibly results from a blend of hair-raising and scary.
Etymology from Wiktionary, CC BY-SA