b.Military. eighth-wheel, when a body of troops revolves upon its centre or one of its ends to the extent of one-eighth part of a circle.
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1796 Instr. & Regulations Cavalry 130 According to the degree ordered, whether half, quarter, or eighth wheel.
1796 Instr. & Regulations Cavalry 144 The eighth wheel is toward the flank which is to be the head of the column..advantage will arise if the eighth wheel is made on the center of each body.