Lichtenstein espoused it as an interest outside work (3,3)

I believe the answer is:

pop art

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(Other definitions for pop art that I've seen before include "Work done by Warhol" , "Apt pro (anag.)" , "Warhol's style" , "Marilyn Diptych, perhaps" , "Artistic movement influenced by commerce and the mass media" .)

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