1. Lacking any complex internal structure."That bitty box has only a flat file system, not a hierarchical one."The verb form is flatten.Usually used pejoratively (at least with respect to file systems).2. Said of a memory architecture like that of the VAX or Motorola680x0 that is one big linear address space (typically with each possible value of a processor register corresponding to a unique address).This is a Good Thing. The opposite is a "segmented" architecture like that of the Intel 80x86 in which addresses are composed from a base-register/offset pair.Segmented designs are generally considered cretinous.3. A flat domain is one where all elements except bottom are incomparable (equally well defined).E.g. the integers.[Jargon File]