RhymeZone: tournaisian definitions

Definitions of Tournaisian:

noun: (geology) In the ICS geologic timescale, the lowest stage or oldest age of the Mississippian, the oldest subsystem of the Carboniferous. It lasted from 358.9 Ma to 346.7 Ma and was preceded by the Famennian and followed by the Viséan.

(Definitions from Wiktionary)