To isolate means to contain or withhold within a certain boundary. Nothing goes in, nothing goes out. Whatever is being isolated is protected. Isolate definition, to set or place apart; detach or separate so as to be alone. See more. De- isolate definition, to remove from isolation. See more. Microbiology A population of microorganisms or viruses that has been isolated. Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Such a difference would produce a dialect in case of isolation. Examples from the Web for isolation Expand. Abbreviations Definitions Phrases References Symbols. Don't get us started on 'bimonthly'.