Replace-by-fee (RBF) is a method that allows to replace one version of an unconfirmed transaction with a different version of the transaction that pays a higher transaction fee. It was proposed in BIP125 and the initial implementation was released in Bitcoin Core 0.12.0.
Replace-by-fee with Trezor in Electrum
Trezor Wallet does not support Replace-by-fee method yet.
It is possible to use Replace-by-fee with Trezor device in Electrum. The original transaction can be replaced only if it was made using Electrum with the "Replace by fee" option on (Tools - Preferences - Replace by fee).
See also Child Pays For Parent (CPFP)