I don't know exactly what the implication would be in terms of handbags, but the following would be my empricial observations about a 'cabas'

As alajaponaise has said, it is usually something that tends to gape open, the classic kind of (often rush-woven or similar) shopping bag.

It is NOT usually flat, which is why it is not really the same as a carrier bag etc.

And it is certainly not rigid, which rather rules out basket, I feel.

Here's a fancy Vuitton version!

http://www.momist.com/blog/2005/12/louis-vuitton-globe-shopp...

Note that the Vuitton (and some others) refer to it as a 'shopper' when talking about the handbag version.

And here's the more 'classic' version:

http://images.google.com/imgres?imgurl=http://www.provence-o...

Try a Google IMAGE search for loads of examples!



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Note added at 17 hrs (2006-05-23 08:40:34 GMT)
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Thanks to Rachel's alert, I've realized the above truncated links won't work. Here's a different link to the same Vuitton style:

http://www.purseblog.com/brands/louis-vuitton/louis-vuitton-...



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Note added at 17 hrs (2006-05-23 08:44:05 GMT)
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And here's the Provence outillage one for the traditional rush-woven shopper:

http://www.provence-outillage.fr/detail.asp?id=1394&idprod=3...

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Note added at 17 hrs (2006-05-23 08:45:11 GMT)
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These last 2 links SHOULD work, if you click on them directly --- even though the link LOOKS truncated, the hover-over confirms it is OK