According to Chelan County, WA a short subdivision aka Short Plat is the division of land into four or fewer lots, plots, sites, parcels, or tracts.  note: examples are based on Chelan County Code but, the same principles are used in all counties.

This means that if a parcel of land's current designation or zoning allows for division of land, then a person can go through the short plat process and achieve this division.  Example:  A 10 acre parcel, zoned RR2.5 or 2.5 acre min lot size, can be short subdivided into four separate lots each with separate parcel numbers.  As you can see this can create equity.  Note:  Zoning designations can be different in different counties, cities and states, check with a professional or local agencies to find out the current zoning for a specific property. 

This process is commonly thought of as dividing a large plat of land but, this same process can be used in Urban areas. 

Example No. 2 - A 20,000 sq. ft. lot, zoned UR3 (Urban Residential 3) Chelan County, can be divided into four, 5,000 sq. ft lots or 7,000 sq. ft.  lot  with a duplex. 

Before anyone should attempt this process they should contact a land use planning consultant and determine possible development costs, problems that may exist and most importantly the marketability of the project.