In other words, B flat thirteenth with a flat ninth.

B flat is the root. The seventh is A flat, the ninth is C, the eleventh is E flat and the thirteenth is G. So this chord has a G at the top and the ninth is flat, which means a C flat (enharmonically a B natural). This creates a lovely diminished sound, with the conjunction of B flat and B natural (= C flat). This is Coltrane getting modal.

The same chord, based on C rather than Bb, can be seen here (second chord in the gallery); in this case the eleventh is played too, but it may be left out:
https://en.wikipedia.org/wiki/Thirteenth#Gallery

"Bb13b9 = Bb half/whole diminished scale"
http://www.jazzguitar.be/forum/improvisation/2326-naima-chan...

Coltrane uses it in Giant Steps:

"Fm7 Bb7 Ebmaj7 C#m7 F#7
Fm9 Bb13b9 Eb6/9 C#m11 F#13 repeat from beginning"
http://www.musiclassroom.com/partitions/Coltrane_giant__tep_...

--------------------------------------------------
Note added at 1 hr (2015-09-23 15:16:49 GMT)
--------------------------------------------------

If you play the whole thing with the eleventh as well you have another minor ninth dissonance between the third (D) and the eleventh (Eb). It sounds quite strange. But the flat ninth is a really beautiful effect.

Ninths, elevenths and thirteenths, with various alterations, are staple harmonies in jazz. Previously, in early twentieth-century "classical" music, Ravel in particular used them to marvellous effect.

--------------------------------------------------
Note added at 2 hrs (2015-09-23 15:45:01 GMT)
--------------------------------------------------

By the way, the discussion in my second reference (www.jazzguitar.be) is very interesting. They go on to discuss the half/whole diminished scale implied by this chord. In Bb this scale would be:
Bb B Db D E F G Ab
The flat ninth Cb, as I said, is enharmonically a B.

--------------------------------------------------
Note added at 23 hrs (2015-09-24 13:38:01 GMT)
--------------------------------------------------

"Accord enrichi": that's a harder question than the first one! It definitely doesn't mean augmented, though an augmented chord would be one example of an "accord enrichi".

The trouble is that the common terminology in the two languages doesn't match, unfortunately. In French an "accord enrichi" is any chord with something added to the basic triad. An ordinary (minor) seventh is already an "accord enrichi". But in English we commonly talk about either "extended chords" or "altered chords". Both of these are "accords enrichis", but they don't include all "accords enrichis": there are some of the latter that are neither extended nor altered. An extended chord is a chord with one or more notes added beyond the seventh: ninths, elevenths and thirteenths are extended chords. An altered chord is a chord with one or more notes altered from the diatonic note to a neighbouring note in the chromatic scale: sharpened or flattened, to put it simply. Augmented and diminished chords are both altered. So the chord you were asking about in this question is both extended (it's a thirteenth) and altered (it has a flat ninth).

But that doesn't exhaust "accords enrichis". A chord with a suspended fourth or added sixth (both common) is enrichi, but it's neither extended nor altered.

I think what you should do is use the literal "enriched chord" for this. It's not common, but it's sometimes used; here, for instance:
https://books.google.es/books?id=MYB8DmNL2XYC&pg=PA28&lpg=PA...

I think it's the best option for you here. An alternative is "coloured chord", but that's a looser term and in practice not quite so broad, in my opinion.