WORD OF THE DAY

arrant
1. Complete, utter - what arrant nonsense
2. Being notoriously without moderation

errant
1. Erring or straying from the accepted course or standards - errant values (often used humorously)
2. Not in the right place; having moved from the correct position - an errant strand of hair
3. Travelling in search of adventure - a knight errant

From Merriam-Webster:

The earliest sense of both errant and arrant was “traveling or given to traveling.” Etymologists believe that arrant came to take on its current meaning, "utterly bad," from the frequency with which this "traveling" sense of arrant modified words like thief (as in "a vagabond or wandering thief"). Errant, meanwhile, took on the additional meanings of “fallible,” “behaving wrongly,” and “straying.”

Of Oxford's twenty example sentences using "arrant" (linked at the definition above) every single one uses the phrase "arrant nonsense." This may be its only contemporary use.