Definitions for "Thyratron"
It is a hot-cathode tube (gas filled), where one more control electrodes initiate, but it never limits or interrupts the flow of electrons.
A gas-tube rectifier with a grid electrode that has the ability to initiate current flow when the anode is positive. Once conduction occurs, the grid loses control until the plate current is interrupted.
a gas-filled multielement tube with a hot cathode