What is plural noun for mother-in-law?

in "people in peace, not profit and war" chrisholm uses inductive reasoning for her argument against defense spending by stating that the new administration, like most americans, wanted to invest in social objectives, so they must not want to prioritize defense spending. mr. nixon said "we can delay no longer in launching new approaches to the problem that beset them", but chrisholm points out that the programs were delayed anyways.