WordWeb Online

1. Of an appropriate or pertinent nature

1. At an opportune time
   "your letter arrived apropos";
   - seasonably, timely, well-timed
    
2. Introducing a different topic
   - by the way, by the bye, incidentally

1. With regard or relation to; on the subject of
   "I have a query apropos your previous reply";
   - regarding, concerning, about, respecting, re, as regards, with regard to, as for, as to, in connection with

See also: apposite, appropriate, appropriateness, apt, pertinent

Antonym: malapropos

Encyclopedia: Apropos