Correct spelling for the English word "mesoomentum" is [mˌɛsuːmˈɛntəm], [mˌɛsuːmˈɛntəm], [m_ˌɛ_s_uː_m_ˈɛ_n_t_ə_m] (IPA phonetic alphabet).
I apologize, but "mesoomentum" does not appear to have an established meaning or definition in the English language. It is possible that the term is either very obscure or non-existent. Dictionary definitions are typically available for words that have been widely used and recognized by the majority of English speakers.
If you have any other word or term you would like me to provide a definition for, please let me know and I would be happy to assist you.
The attachment of the omentum.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.