(manner) In a serious or literal manner.
He was hoping that we would take him seriously.
Gravely; deeply; very much.
That was a seriously unpleasant thing to say.
Used to attempt to introduce a serious point in a less serious conversation
Now, seriously, why did you forget to feed the cat today?
Used to call back to a previous point, either in disbelief or emphasis
You baked 10 cakes. Seriously, why did you do that?