Being at once opportune and to the point.
1. At an appropriate time; opportunely.
2. By the way; incidentally: Apropos, where were you yesterday?
prep. With regard to; concerning.
[French à propos : à, to (from Old French a, from Latin ad-; see ad-) + propos, purpose (from Latin prpositum, neuter past participle of prpnere, to intend; see propose).]