As adverbs the difference between massively and vastly
is that massively is in a massive manner, in a way that appears large, heavy or imposing while vastly is greatly, in a vast manner.
massively
English
Adverb
(
en adverb)
In a massive manner, in a way that appears large, heavy or imposing.
(slang) Greatly.
vastly
English
Adverb
(
en adverb)
Greatly, in a vast manner.
*{{quote-book, year=1913, author=
, title=Lord Stranleigh Abroad
, chapter=1
citation
, passage=“I have visited my quarters, and find them very comfortable.
Synonyms
* exceedingly, extremely, highly, immensely, supremely, tremendously