The term 'archaic preposition' refers TO a type of preposition that is no longer commonly used in modern English. The three crossword solutions for this term are 'thro, ' 'ERE, ' and 'unto, ' all of which are four-letter words. 'Thro' is an old form of the word 'THROUGH, ' meaning 'from one side or point TO the other.' 'ERE' is an old form of the word 'BEFORE, ' meaning 'at an earlier time.' Lastly, 'unto' is an old form of the word 'TO, ' meaning 'in the direction of.'