Abbreviation of Missus or Mistress (“used before an adult woman's name or surname, used for any high-status woman without regard to marital status until the 1800s, after which it began to be reserved for married, divorced and widowed women and used with their married surnames”)
"The study used MRS to analyze the chemical composition of the brain tissue without using ionizing radiation."
Initialism of magnetic resonance spectroscopy.
In plain English: Mrs is an old-fashioned way of saying Mrs, which you use as part of someone's name to show they are married women.
"She introduced herself to her neighbors with confidence, stating clearly that she was Mrs. Gable now."
Initialism of Materials Research Society.
"The paper was published in Mrs, where researchers shared their latest findings on nanomaterials."