The opposite of high key. Basically just not very showy. If someone thinks you are low key kinda hot, it means that they find you quite attractive but you are very subtle about being attractive. You almost don't know it.
to keep something lowkey: to not announce it; to have a quiet gathering; opposite of a large party or big group of people; not much emphasis, closely aligned with a normal night out doing the usual stuff.
im going out tonight but it's pretty low key; i've gotta work tomorrow so tonight's going to be a low key event.
A word to describe a state of keeping on the low and not to have your name in everyones mouth. Low key is also a state of which someone does not want to be talked about or be heaty.
for example if someone is too heaty or has too much beef and is too "known" they might get advice to keep low key for a while