IPA: /ˈærəntli/
KK: /ˈærəntli/
In a complete or absolute way; used to emphasize something negative or undesirable.
He was an arrantly dishonest person, always lying to get what he wanted.
Arrantly is derived from the adjective "arrant" (from Old French *arrant*, meaning 'to be present' or 'to be in a state'), which is often used to emphasize a negative quality. The suffix "-ly" (meaning in a manner of) is added to form an adverb. Thus, "arrantly" means in a manner that is completely or utterly, often with a negative connotation.
Think of 'arrant' meaning completely or utterly, and remember that 'arrantly' describes doing something in that complete manner.