Dynamic: Dynamic fee control means that the mobile Bitcoin wallet service will suggest an amount, based on network conditions at the time you make the transaction. (coinstaker.com)
BitGo implemented dynamic fees in July 2015 and now, two years later, we are still working on improving our fee estimate algorithms. (getrevue.co)
Other exchanges such as HitBTC have introduced the same sort of dynamic fee schedule in recent months. (cryptoninjas.net)