1
general::
For all time, forever, as in This land was given to the state in perpetuity. [First half of 1400s]
American Heritage Idioms
2
general::
Phrase(s): in perpetuity
for an indefinitely long period of time; eternally. • My trust fund generates income in perpetuity. • The right for the road to cross my land was granted in perpetuity to the county.
McGrawhill's American Idioms And Phrasal Verbs