Without feet or footrests; lacking a proper foundation or support; lacking sense or validity.
From 'foot' plus '-less' suffix meaning 'without.' Used literally for creatures without feet, and figuratively since at least the 17th century for baseless arguments.
A footless argument is one that can't stand on its own—the metaphor from literal feet to intellectual grounding is so perfect that footless has meant 'senseless' for centuries.
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