(in AM, use somber)
1) ADJ-GRADED If someone is sombre, they are serious or sad.

The pair were in sombre mood...

His expression became increasingly sombre...

Unfortunately, this happy story finishes on a more sombre note.

serious, solemn
Derived words:
sombrely ADV-GRADED ADV after v, ADV adj

`All the same, I wish he'd come back,' Martha said sombrely...

She felt more sympathy for Neil's sombrely stolid manner than she ever had before.

2) ADJ-GRADED Sombre colours and places are dark and dull.

...a worried official in sombre black...

It was a beautiful house, but it was dark and sombre and dead.

English dictionary. 2008.