backbreaking
/ˌbækˈbreɪkɪŋ/Definitions
1. adjective
causing or resulting in severe physical or mental strain; exhausting or demanding
“The backbreaking labor on the farm was a major factor in their decision to retire early.”
2. noun
an activity or situation that is backbreaking
“The backbreaking work of manual labor in the city’s construction industry sparked a union strike.”