i've said this twice now.

se·ri·ous Pronunciation Key (sîr-s)
adj.
Grave in quality or manner: gave me a serious look.

Carried out in earnest: engaged in serious drinking; serious study of Italian.
Deeply interested or involved: a serious card player.
Designed for and addressing grave and earnest tastes: serious art; serious music.
Not trifling or jesting: I'm serious: we expect you to complete the assignment on time. Her question was serious enough to deserve a thoughtful response.
Of considerable size or scope; substantial: a cleanup that cost serious money.
Of such character or quality as to appeal to the expert, the connoisseur, or the sophisticate: “Every serious kitchen needs at least one peppermill” (Washington Post).
Concerned with important rather than trivial matters: a serious student of history.

Being of such import as to cause anxiety: serious injuries; a serious turn of events.
Too complex to be easily answered or solved: raised some serious objections to the proposal.