Nippy describes two related sensations of sharpness:

When the weather feels nippy, the air has a biting cold that makes you want to pull your jacket tighter or rub your hands together. A nippy morning in October might have frost on the grass and a wind that stings your cheeks. The cold doesn't just feel cool: it has a sharp, attention-getting quality that makes your nose tingle and your breath visible.

The word can also describe animals that like to bite or nip. A nippy dog might playfully snap at your heels, and a nippy crab at the beach could give your toe a quick pinch if you get too close. The connection between both meanings is that sense of something quick and sharp, whether it's cold air that bites at your skin or a creature that literally bites.

You might hear someone say, “It's a bit nippy out there!” as a friendly warning to grab a sweater before heading outside. The word has a lighter, almost cheerful tone compared to saying it's “freezing” or “frigid.” Nippy suggests cold that's brisk and invigorating rather than dangerously harsh.