Naver defines '썸타다' as:
have a fling
The action of pushing and pulling when a man and a woman who are attracted to but haven't started seeing each other.
These seem to be different meanings. The first meaning - 'a fling' is a complete (consummated?), but short, relationship, while the second meaning hints at a point in the development of a relationship. Are these both reasonable translations?
What is the origin of the term? I've heard that 썸 is from the English 'something', while 타다 is to 'get on' or 'ride'. Do these give clues to the meaning? (They seem to hint at the 'fling' meaning!)