plural noun

: a hypothetical group ancestral to placental mammals postulated to have reached a stage of development equivalent to that of the marsupials
in some classifications : a group coextensive with Marsupialia

Word History


New Latin, from meta- + -theria

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

  • More than 250,000 words that aren't in our free dictionary
  • Expanded definitions, etymologies, and usage notes
  • Advanced search features
  • Ad free!

Dictionary Entries Near Metatheria

Cite this Entry

“Metatheria.” Dictionary, Merriam-Webster, Accessed 10 Dec. 2023.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!