Unusual, a.
Not usual; uncommon; rare; as, an unusual season; a person of unusual grace or erudition. -- Un*u"su*al*ly, adv. -- Un*u"su*al*ness, n.
Shades of meaning
Fernald has no entry of its own for unusual; he lists it under queer, rare.
He lists it without comment; the entries above explain its neighbors.