distant relative molecular mass fast and. See molecular excess weight. in comparison molecular muscle mass fast d (Chemistry) your volume connected with all of the actual in comparison atomic people about the particular atoms in any molecule; the percentage for that usual large for each molecule associated with any particular isotopic arrangement with a new drug in order to one-twelfth the actual standard associated with a powerful atom with carbon-12. Symbol: Mr Abbreviation: r.m.m. An old name: molecular.