When referring to a person in Korean, very rarely is the actual name of the person used. Instead, different titles are applied depending on age, social hierarchy, and family.
A common word that people know is ajumma (아줌마). This roughly translates to something like an older woman or married woman, however, you have to be careful when to use it.
Calling someone who is obviously not someone old can be very offensive and is almost the equivalent of a curse word. Even if someone looks older, you still would only want to use this word for someone you know is in their late 60s and up. Also, even though the word has a meaning of married woman, you wouldn’t want to call a woman who is married in her 20s or 30s ajumma.
Some more respectful terms you could use are:
아주머님 (a-ju-meo-nim) = Sounds similar to 아줌마 but is more polite and has an added “-님” which makes titles of people sound polite.
어머님 (eo-meo-nim) = This is used to refer to someone else’s mother and can be used in a polite manner as well.
Finally, the word 할머니 (hal-meo-ni) is also used, especially by kids, to refer to an old lady. This word means grandma, but has evolved to take on another meaning as well.
When in doubt, it’s best to use 아주머님 or 할머니 to be respectful and polite when addressing an older lady.