groundbreaking
US: /ˈɡɹaʊnˌbɹeɪkɪŋ/, /ˈɡɹaʊndˌbɹeɪkɪŋ/
UK: /ɡɹˈaʊndbɹeɪkɪŋ/
UK: /ɡɹˈaʊndbɹeɪkɪŋ/
Advanced English dictionary
+ adjective
[only before noun] making new discoveries; using new methods: a ground-breaking report / style
groundbreaking