Authoritative

Part of speech: adjective (a.)

1. Having, or proceeding from, due authority; entitled to obedience, credit, or acceptance; determinate; commanding. The sacred functions of authoritative teaching. Barrow.

2. Having an air of authority; positive; dictatorial; peremptory; as, an authoritative tone. The mock authoritative manner of the one, and the insipid mirth of the other. Swift. -- Au*thor"i*ta*tive*ly, adv -- Au*thor"i*ta*tive*ness, n.