Gravity
Solemnity, Severity, Seriousness
noun, な adjective
If everyone is acting solemn and strict then you should probably pay special attention to the gravity of the situation you're in. Don't start playing the trumpet when you're supposed to be bowing your head!
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
結果を厳粛に受け止め、次回に臨みたい。
I want to solemnly react to the results and face it next time.