The Concise Oxford Dictionary:
1. favouring, encouraging or enforcing strict obedience to authority as opposed to individual freedom;
2. tyrannical or domineering.
-n. a person favouring absolute obedience to a constituted authority
1. Being recognized as true or dependable
2. (of a person, behaviour etc.) commanding or self-confident
3. official, supported by authority
From today's Financial Post, the following:
"Blais, who is known for an authoritative leadership style, steered the CRTC on a consumer-friendly agenda that often rankled big businesses. Some believe he has a shot at an extended term even though he was appointed by the Conservatives, given his positive relationship with the heritage department."