treadless

/ˈtrɛdləs/
adjective
  1. Having no tread; smooth and lacking the ridges that provide grip, usually referring to tires or shoe soles.
    • The treadless tires were dangerous on the wet road.
    • Driving on treadless tires is illegal in many states.
    • His shoes were so treadless that he slipped on the polished floor.
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