What are some words that describe Banquo in Shakespeare's Macbeth?

Macbeth gives an accurate description of Banquo in his soliloquy in Act 3, Scene 1.

Our fears in Banquo
Stick deep, and in his royalty of nature
Reigns that which would be fear'd. ’Tis much he dares,
And, to that dauntless temper of his mind,
He hath a wisdom that doth guide his valor
To act in safety. There is none but he
Whose being I do fear; and under him
My genius is rebuked, as it is said
Mark Antony's was by Caesar.

Banquo has a noble bearing and a noble mind. He is daring and dauntless, that is, fearless and determined. Most importantly, "He hath a wisdom that doth guide his valor / To act in safety." Banquo is wise and prudent. He is a keen observer and a deep thinker, but he keeps his thoughts to himself. When Macbeth compares himself to Mark Antony and Banquo to Octavius Caesar, he is showing how he and Banquo differ. Macbeth, like Antony, is emotional and impulsive, whereas Banquo is cool, calculating, patient, practical, cautious, and determined. Octavius Caesar ended up becoming sole ruler of the Roman world because of his stronger character. Antony was intelligent and courageous, but he loved pleasure and dissipation. While he was indulging in all sorts of sensual pleasures, Octavius was thinking, planning, studying, forming alliances, and so on. It was inevitable that he would end up the sole survivor of the triumvirate that was formed by Antony, Lepidus, and Octavius after the assassination of Julius Caesar.

Macbeth senses that Banquo is a constant threat. Banquo could be planning to kill Macbeth just as Macbeth killed King Duncan. This is one of the reasons Macbeth suffers from insomnia and from terrible nightmares. How can he go to sleep when somebody might be planning to slip into his room and cut his throat? He says in an earlier soliloquy:

But in these cases
We still have judgement here, that we but teach
Bloody instructions, which being taught return
To plague the inventor. This even-handed justice
Commends the ingredients of our poison'd chalice
To our own lips.     I.7

If he can become king by killing Duncan, then somebody else can become king by killing him. And Banquo is the most likely suspect, since the Weird Sisters, who predictions have thus far all come true, have foretold that Banquo would be the sire to a whole line of Scottish kings. Macbeth is afraid of Banquo because Banquo is, above all, intelligent, patient, and inscrutable. Macbeth knows that Banquo must be thinking about the possibility of having his descendants inherit Macbeth's throne. And he is correct. Banquo says to himself in secret:

Thou hast it now: King, Cawdor, Glamis, all,
As the weird women promised, and I fear
Thou play'dst most foully for't: yet it was said
It should not stand in thy posterity,
But that myself should be the root and father
Of many kings. If there come truth from them—
As upon thee, Macbeth, their speeches shine—
Why, by the verities on thee made good,
May they not be my oracles as well
And set me up in hope? But hush, no more.   III.1

Macbeth shares all his thoughts with his wife, but Banquo shares his thoughts with no one but himself. This is a sign of worldly wisdom, but it takes great strength of character to keep one's own counsel.