I don't quite know what this sentence means, but something about it makes me feel unutterably sad.

She found something unutterably sad about it, and she couldn't exactly figure out why.

Watching the intensifying fight, So-Peng felt himself grow unutterably sad.

There was something unutterably sad about that.

There was something unutterably sad and poetic about these wounded men enduring more pain to pay homage to their dead.

When they knew each other, it was unutterably sad for them to meet.

A tearful, fumbling, unutterably sad affair which had left both of them plagued with guilt for months afterwards.

The angel looked unutterably sad as he studied me, then seemed to rally a little.

The unutterably sad sound of the sparrow lingered in his ears.

And I looked up to see his face unutterably sad.