Apropos, a. & adv.
Etymology: [F. ad) + propos purpose, L. proposium plan, purpose, fr. proponere to propose. See Propound.]
1. Opportunely or opportune; seasonably or seasonable. A tale extremely apropos. Pope.
2. By the way; to the purpose; suitably to the place or subject; -- a word used to introduce an incidental observation, suited to the occasion, though not strictly belonging to the narration.
Shades of meaning
Fernald lists apropos only as an antonym, under alien.
He lists it without comment; the entries above explain its neighbors.
Synonyms
none given