Open English Wordnet
Nouns
(n)attributive genitive, attributive genitive casea word in the genitive case that is used as an attributive adjective“an example of the attributive genetive is `John's' in `John's mother'”
Adjectives
(s)attributive genitivea word in the genitive case used as an attributive adjective“an example of the attributive genitive is `John's' in `John's mother'”