Dictionary.com
Thesaurus.com

parent-in-law

American  
[pair-uhnt-in-law, par-] / ˈpɛər ənt ɪnˌlɔ, ˈpær- /

noun

plural

parents-in-law
  1. the father or mother of one's spouse.


Etymology

Origin of parent-in-law

First recorded in 1850–55: parent, in, law 1