Definition (full): insidious, deceitful, tracked by footprints
Strong's Exhaustive Concordance
From aqab; in the original sense, a knoll (as swelling up); in the denominative sense (transitive) fraudulent or (intransitive) tracked -- crooked, deceitful, polluted.
KJV: Every valley shall be exalted, and every mountain and hill shall be made low: and the crooked shall be made straight, and the rough places plain:
NASB: "Let every valley be lifted up, And every mountain and hill be made low; And let the rough ground become a plain, And the rugged terrain a broad valley;