Very cold with frost, or unfriendly and distant in manner toward someone.
From Old English 'frost' (frozen water crystals) plus 'y' (becoming an adjective). By the 1500s, the metaphorical meaning of 'cold and unwelcoming' emerged from the literal temperature sense.
Your skin actually becomes less sensitive to warmth and touch when it's frosty outside—the cold triggers the same receptors that frosty personalities activate (social rejection literally feels physically cold, as brain scans show).
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