I like that word seonbae = 선배. This is the word you can often hear frim Boys before flowers. You use it to respect your senior. For example, someone who has graduated from the same school but earlier than you and older people and i heared that it is really used a lot in koresn university in order to show your respect to older students. And i think what you mean by you are dead in korean is chukneunda = 죽는다. I agree with you that i can hear the word quite a lot from korean dramas or movies. I will write down some sample sentences which may help you understand. First of all 너 죽는다 is a basic and simple sentence which means you are dead. 너 그렇개 하면 죽는다 = if you do that , you re dead (it is commonly used as a joke) 너가 죽는다고 해결될일이 아니야 = killing yourself is not going to solve the problem Hope this helps :)

선배(先輩) - seonbae you can call someone who elder then you，your senior (at work, at university, ect.)

i'm not yet familiar with hangul but i think Sunbae means an order of respect. It's a term used for someone older than you, someone senior than you, usually an elder. :)