Cold or chilled; an archaic or poetic way of describing something as being in a cold state.
From Old English 'a-' (prefix intensifier) combined with 'cold,' creating a strengthened form meaning very cold or intensely cold.
You'll find 'acold' in Shakespeare and old poetry because the 'a-' prefix was used to intensify adjectives in Middle English, making 'acold' sound more dramatic than plain 'cold'—it's like saying 'stone cold' today.
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