Alternative forms 
- erraunt (obsolete)
- straying from the proper course or standard, or outside established limits
- prone to making errors
- (proscribed) utter, complete (negative); arrant
Usage notes 
Sometimes arrant (“utter, complete”) is considered simply an alternative spelling of errant, though many authorities distinguish them, reserving errant to mean “wandering” and using it after the noun it modifies, notably is “knight errant”, while using arrant to mean “utter”, in a negative sense, and before the noun it modifies, notably in “arrant knaves”.
Etymologically, arrant arose as a variant of errant, but the meanings have long since diverged. Both terms are archaic, primarily used in set phrases (which may be considered cliché), and are easily confused, and on that basis some authorities suggest against using either.
- (utter, complete): arrant (generally distinguished; see usage)
Derived terms 
- “arrant/errant”, Common Errors in English Usage, Paul Brians
- On Language: Arrant Nonsense, William Safire, January 22, 2006, New York Times
- Merriam–Webster’s dictionary of English usage, 1995, “errant, arrant”, pp. 406–407
- Present participle of errer.
- third-person plural present active indicative of errō