But that's the point. It doesn't describe it; it is simply wrong. In fact, "large ball," even if the Hebrew for "ball" denoted a toy, would be more accurate, at least by analogy, than "circle." "Circle" is, in every sense, wrong.
This, of course, also doesn't explain the errors regarding the earth being immovable, and describing the earth's supposed "corners" and "foundations." Not to mention trees and mountains so high they could be see or see, the furthest reaches of the earth.
That these are all perfectly consistent with a flat-earth cosmology of the kind common in the ancient Mideast (and wholly inconsistent with twenty-first century knowledge) should not be at all remarkable. They, and their writings, were products of their age.
Isa 40:22I've underlined the word word for "circle" [chuwg] (Strong's 02329). Here are the only other verses that use the same word, none of which implies a "sphere":
[It is] he that sitteth upon the circle of the earth, and the inhabitants thereof [are] as grasshoppers; that stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in
Job 22:14Word Search Results for "sphere" -- NONE
Thick clouds [are] a covering to him, that he seeth not; and he walketh in the circuit of heaven.Pro 8:27
When he prepared the heavens, I [was] there: when he set a compass upon the face of the depth
Word Search Results for "ball " [duwr] (Strong's 01754). Here are all verses that use the word for "ball" [NOTE: Two are in the same book as the "circle of the earth" passage, so the author of Isaiah had both words at his disposal]:
Isa 22:18
He will surely violently turn and toss thee [like] a ball into a large country: there shalt thou die, and there the chariots of thy glory [shall be] the shame of thy lord's house.Isa 29:3
And I will camp against thee round about, and will lay siege against thee with a mount, and I will raise forts against thee.Eze 24:5
Take the choice of the flock, and burn also the bones under it, [and] make it boil well, and let them seethe the bones of it therein.
[The Hebrew lexicon gives this meaning as "a burning pile, a round heap of wood"]