mon ‧ u ‧ ment ‧ al /ˌmɒnjəˈmentl◂, ˌmɒnjʊˈmentl◂ $ ˌmɑː-/ BrE AmE adjective
1 . [usually before noun] a monumental achievement, piece of work etc is very important and is usually based on many years of work:
a monumental contribution to the field of medicine
Charles Darwin’s monumental study, ‘The Origin of Species’
2 . [only before noun] extremely large, bad, good, impressive etc:
Banks and building societies were yesterday accused of monumental incompetence.
a monumental task
There was a monumental traffic jam on the freeway.
3 . [only before noun] relating to a monument or built as a monument:
a monumental arch