n. overlord, lord, king, master, tyrant, someone who rules absolutely; lordship, position of being overlord; rule, tyranny

Sahrot thur qahnaraan.
The mighty overlord is vanquished
(Dragon, 0009E075)

And so Alduin's lordship passes to you. Thuri, Dovahkiin. I gladly submit to your mastery of the Thu'um.
Thuri, Dovahkiin = “(You are) my king/overlord, Dragonborn”
(Odahviing, 0009C20F)

Daar sul thur se Alduin vokrii.
This day the overlordship of Alduin (is) restored.
(Dragon, 00078DF7)

Alduin mah nol thur.
Alduin (has) fallen from (the) overlord(ship).
(Odahviing, 000E16FD)

Yes. There were a few of us that rebelled against Alduin's thur... his tyranny. We aided the humans in his overthrow.
(Paarthurnax, 0003FA41)

Someone who rules absolutely, as from strength and domination. A person to whom all loyalty  is owed, not as a matter of oaths but the natural order of rule. Only the strongest can be named thur.

Featured prominently in the dragon name Paarthurnax ‘ambition overlord cruelty’.