is serious about it; means it seriously
So als ob er es ernst meint.
As if he were serious.
— Léon - Der Profi (1994)
Die wissen, dass Tom es ernst meint.
They know that Tom is serious.
Manchmal ist es schwer zu erkennen, wann Tom es ernst meint.
Sometimes it's hard to tell when Tom is serious.
Jemand, der es ernst meint.
Someone who is serious about it.