downdate

It will require a downdate and filing as we consummate the netting agreement.

The idea of a retronym is to downdate: to modify a familiar term in a way that calls attention to its not being the updated version.

(Don't look up downdate : I can't wait for the dictionaries.)

Rank-one downdate

A rank-one downdate is similar to a rank-one update, except that the addition is replaced by subtraction: .

The code for the rank-one update shown above can easily be adapted to do a rank-one downdate: one merely needs to replace the two additions in the assignment to and by subtractions.