총각(Chongkak) - Single man(Bachelor)
처녀, 총각 are basically unmarried single woman and man. 미혼녀(Mihonnyeo), 미혼남(Mihonnam) are the same words as 처녀, 총각.
Here 녀(Nyeo) is woman, and 남(Nam) is man.
노처녀(Nocheonyeo) - Old bachelorette
노총각(Nochongkak) - Old bachelor
Many Korean people think that marriage is a very important thing in your life. If you are not married even after you turn 30, people around you start to say things like, "When are you gonna get married?" "Do you have someone to marry?" "Do you have a boyfriend/girlfriend?" "You need to start thinking about getting married seriously!"
So, many old bachelors or bachelorettes get stressed out whenever people say things like that to them.
노처녀, 노총각 don't have any starting age.
Even only 20 years ago, people consider women over 27 노처녀 and men over 30 노총각.
However, now, people think that women over 35 are 노처녀 and men over 40 are 노총각. But, everyone thinks differently. Some might think that a woman who is 31 years old is 노처녀 and some might not.
Once you get married, you become 기혼녀(Kihonnyeo), 기혼남(Kihonnam) or 유부녀(Yubunyeo), 유부남(Yubunam)
There are some slang words for these. Recently people have started to use 품절녀(Pumjeolnyeo), 품절남(Pumjeolnam) for married woman and man. 품절 means 'Sold out.' Basically, it is sold out or taken, so that the person is not available anymore.
There are some hoodies with 품절녀, 품절남 written on. You might want to wear them on your honeymoon.
Check these videos about 노총각 and 노처녀.
(Go to 1:25 to see the 노총각 part)
One thing that you should know about Korean culture is most Korean people think that older son or daughter should get married before younger ones.
The younger brother of 노총각 wants to get married, but since his older brother doesn't have any girlfriend and doesn't seem to get married any time soon, the younger brother gets frustrated and worries that his girlfriend might break up with him out of impatience.
Lots of 노총각, 노처녀s are complaining that their relatives are the ones that put the most pressure on them about marriage. So, holidays when families and relatives gather are the time that 노총각, 노처녀 are not really happy.