Lacking or absent; in a state of want or deficiency.
From ā- (prefix) + wanting (present participle of want, from Old English wanian meaning 'to lack'). The prefix intensifies the sense of absence or need.
The 'a-' prefix in old English (like in 'awanting,' 'afire,' 'asleep') originally meant 'in a state of'—it's why we still say 'alight' (in a state of being lit) instead of just 'lit.'
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