In plain words
The poet, to the Lord of Araṅgam: O you whose greatness the matchless one with the bull [Rudra] and the four-faced one [Brahmā] cannot know, O First Cause [of all], who are yourself every world without exception and are the three letters [Om]: on the day when the men of Yama reckon that this man's span is over and set about seizing me so that I tremble, on that day you must protect me, O you who sleep on the serpent couch in Araṅgam.