Longman Dictionary of Contemporary English - serious

~ adj 1 »SITUATION/PROBLEM« a serious situation, problem, accident etc is extremely bad or dangerous  (a serious illness | How serious do you think the situation is? | serious crime)  (The number of serious crimes has increased dramatically in the last year.) 2 be serious a) if someone is serious about something, they say what they really mean and are not joking or pretending + abou  (I stopped laughing when I realized Jen was serious about it.) I'm serious! spoken (=used to emphasize that something is important)  (I'm serious, Kerry. You'd better listen! | deadly serious (=extremely serious)) b) spoken used to tell someone that what they have just said is silly or impossible  ("We could make it from here to Florida if we drove all night." "Be serious! It's a three day drive." | you can't be serious!)  ("I thought I'd try to fix the car myself." "You can't be serious!") 3 »CAREFUL« careful and thorough  (I think this matter needs serious consideration. | a serious article) 4 »ROMANTIC RELATIONSHIP« a serious romantic relationship is intended to continue for a long time  (Oo, sounds like it's serious!) + abou  (Are you really serious about her then?) serious boyfriend/girlfriend  (Don't even think about Peter. He has a serious girlfriend.) 5 »PERSON« someone who is serious is always very sensible and quiet  (He's a nice guy, but very serious.) 6 »IMPORTANT« important  (They agreed to have lunch before starting on the serious business.) 7 serious money/exercise etc informal a large amount of money etc  (I'll have to do some serious exercise before I can fit into that dress.) 8 »VERY GOOD« only before noun informal very good and often expensive  (He's got some serious stereo equipment!) 9 »SPORT/ACTIVITY« only before noun someone very interested in something, and spending a lot of time doing it  (a serious golfer | Any serious student of psychology should read this article.) 10 »WORRIED/UNHAPPY« seeming slightly worried or unhappy  (You look serious. What's wrong?) - seriousness n