Arrant (adjective)

1. Complete, utter (often used for emphasis).
2. Outright, unmitigated, thoroughgoing, flagrant.

Origin:

Middle english (as a noun denoting a rogue or scoundrel): from old french arrant, present participle of errer "to err", from latin errare. the adjective sense "utter, complete" (late 16th century) probably arose from the notion of "going astray".

Examples:

1. He is an arrant coward.
2. She was an arrant thief who would stop at nothing.
3. The arrant dishonesty of the company was exposed in the investigation.
4. The arrant ignorance of the politician was evident in his speech.
5. The arrant incompetence of the staff was causing delays in the project.