The word "most innumerous" is defined as something that is very scarce or rare. Its antonyms are words that describe abundance, plenty, or numerousness. Some possible antonyms for "most innumerous" are "abundant," "plentiful," "numerous," "prolific," "bountiful," "copious," "excessive," "lavish," "ample," and "overflowing." Depending on the context, other antonyms could include "common," "frequent," "popular," "widespread," or "ubiquitous." Antonyms are important to know because they help us understand the full range of meanings of a word and how it can be used in different contexts.