Said in a kind way it means:

it's too bad, it's a pity

Said in an indifferent way it means:
it's tough, it doesn't matter, I could care less
Example of kind way:
Megan makes terrible hot chocolate, c'est dommage.

Example of indifferent way:
If you don't like my hot chocolate, c'est dommage.
by ray99 September 4, 2009
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