unprepossessing - Dictionary definition and meaning for word unprepossessing
split it as un+possessing. something which you dont want to possess is unattractive.
Un+prepossessing.....If you do not use prepositions properly in your writing it will be unattractive.
un+proposing.... noone would ever propose to a girl who is unattractive/unpresentable.(No offence pls)
If you attract to anything,you will try to preposses it than someone else try before. If it is un(not)+prepossessing means you had not attracted to it.
Unprepossessing and Imposing have similar sounds. Unprepossessing (unattractive) is the opposite of Imposing (impressive).
unprepossessing - focus on 'pre'. If you do not possess some quality or the other before you meet somebody, you cant make good first impression