When now Agenor had his daughter lost,
He sent his son to search on ev'ry coast;
And sternly bid him to his arms restore
The darling maid, or see his face no more,
But live an exile in a foreign clime;
And now his rage, increasing with his pain,
Reddens his eyes, and beats in ev'ry vein;
Churn'd in his teeth the foamy venom rose,
Whilst from his mouth a blast of vapours flows,
Such as th' infernal Stygian waters cast.
speak (about unimportant matters) rapidly and incessantly
And then she cried, "That tongue, for this thy crime,
Which could so many subtle tales produce,
Shall be hereafter but of little use."
Hence 'tis she prattles in a fainter tone,
With mimic sounds, and accents not her own.
"Bereft" also means "unhappy in love; suffering from unrequited love"--this describes how Echo is feeling, but the example sentence is using the adjective to describe how her lovesickness over Narcissus causes her to wander for so long that she is bereft of blood and becomes nothing more than a skeleton with a voice.
Where pining wander'd the rejected fair,
'Till harrass'd out, and worn away with care,
The sounding skeleton, of blood bereft,
Besides her bones and voice had nothing left.
When a person "presumes," he thinks he knows more than he knows, and Pentheus thinks he knows more than a prophet, which leads him to act presumptuously by deriding ("treat or speak of with contempt") the prophet and all the people who worship Bacchus.
Th' unhallow'd Pentheus only durst deride
The cheated people, and their eyeless guide.
To whom the prophet in his fury said,
Shaking the hoary honours of his head:
"'Twere well, presumptuous man, 'twere well for thee
If thou wert eyeless too, and blind, like me:
"Audacious" also means "unrestrained by convention or propriety"--this definition is suggested by the words "impious" and "profane" ("violate the sacred character of a place or language") but since Pentheus does not believe that Bacchus is a god, he audaciously wants to punish the impostor, whom he believes is being audacious ("disposed to venture or take risks") in his kingdom.
Thus did th' audacious wretch those rites profane;
His friends dissuade th' audacious wretch in vain:
In vain his grandsire urg'd him to give o'er
His impious threats; the wretch but raves the more.
"Ghastly" also means "shockingly repellent; inspiring horror"--both definitions are fitting descriptions of the head of Pentheus, which ripped from his body, indicates that he's dead, and in the hands of his spellbound mother, inspires horror in others.
His mother howl'd; and, heedless of his pray'r,
Her trembling hand she twisted in his hair,
"And this," she cried, "shall be Agave's share,"
When from the neck his struggling head she tore,
And in her hands the ghastly visage bore.