Of an appropriate or pertinent nature. (adjective)
Regarding or concerning. (preposition)
By the way. (adverb)
Examples of word apropos
Great tip for beginners and terminal hackers alike, and apropos is installed on a wide number of Linux distros and other terminals.
Writing upon the subject in which he was interested, in the midst of his family, he would pause, pen in hand, to laugh at some jest or say a word apropos of the question under discussion, and return in an instant to his work.
Imagine being Thief of Bagdad, title apropos to these times, as a Chinese American at Graumann's Chinese Theatre, then in its Chinarama phase, chock-a-block with faux orientalism, a chinkee apocalypse in plastic and red paper.
If, for instance, you knew you had a video encoder handy but didn’t quite know how to get at it, type in apropos mpeg and you’ll get a list of commands and programs that have the words “mpeg” in their man, or manual, files.
A final word apropos of post-pop museology: Although this show has just opened, the first edition of the exhibition catalog has already sold out, which proves that an historical show rich in cultural implication can draw people to its concerns.
That's what I get for second-guessing my initial choice of "apropos".
Nothing could be more "apropos" to quote Walter's expression.