back and fill

1 go in contrary directions

2 be indecisive, temporize, vacillate. chiefly North American

☞ The expression was originally nautical: to back is to sail backwards, to fill, to sail forwards (from the notion of the wind filling the sails).

❷2003Commonweal Even as she wants to advance boldly, therefore, she is required by the evidence to back and fill, leaving the reader with a bewildering combination of affirmation and qualification.