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Someone who agrees to do something specific but becomes distracted and goes off in all directions, like Captain Wrongway Peachfuzz
He agreed to take out the trash but then he, being a tangentialist, went through the trash instead, focusing intently on each item, having decided that YOU don't know what constitutes trash, and that he needs to decide.

He micromanages by being a tangentialist, spiraling Brainiac style into the project - trouble is, he misses the target. By a country mile.
by The Debil October 31, 2013