My current favourite Korean word is 서먹서먹하다, meaning to be awkward.
I find Korean words with repeated syllables or phrases easier to remember (and just a little bit cute), they seem to stick in my head better.
Some other examples:
선선하다 to be refreshing (regarding air, wind)
심심하다 to be boring
쌀쌀하다 to be chilly, nippy
답답하다 to be stuffy, tight, constricted
축축하다 to be moist (which I learned from IU’s Marshmallow <3)
눅눅하다 to be humid
통통하다 to be plump
So this is my new vocabulary to practice for this Wednesday. Hopefully I will discover many more words of this type as my Korean progresses ~