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. Informal 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\u201d ( 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.