Most resembling a box in shape; the most square, rectangular, or angular compared to all others.
From 'boxy' plus the superlative suffix '-est', used to describe the maximum degree of a quality among three or more items.
The superlative 'boxiest' is rarely used in everyday speech, which is interesting because superlatives usually beat comparatives—but 'boxiest' just sounds awkward, showing how English speakers naturally avoid clunky words.
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