A person who habitually wastes time, delays unnecessarily, or acts without decisiveness.
From 'dilly-dally' plus the agent suffix '-er' (one who performs the action). The reduplicative base suggests someone stuck in a pattern of circular, time-wasting behavior.
Psychologists now recognize 'dillydalliers' as people who might have decision anxiety—they're not lazy, they're actually stuck in a mental loop of indecision, which makes the old insult more sympathetic!
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