frictionless

adjective2

1. •
   Of or pertaining to lack of friction.

   • It would last many years because of its frictionless bearings.
   • A hard border is a real possibility, and a frictionless border is almost an oxymoron.
2. •
   Of a transaction or trade, without tariffs and non-tariff barriers.

   • "There can be no frictionless trade outside of the customs union and the single market," said Donald Tusk, president of the council of all 28 EU member states. — 2018