In a state of jangling or discordant noise; characterized by clashing, ringing sounds.
From 'jangle' (to make a harsh ringing sound) with the prefix 'a-', which was used in Middle English to create adjectives describing states or conditions.
The prefix 'a-' in English used to be much more productive—you see it in 'aflutter,' 'afire,' and 'ajangle'—but it fell out of fashion, which is why these words sound old-fashioned or poetic to modern ears.
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