- The definition of a substage is a device that supports mirrors and other attachments under the common stage of a compound microscope.
An example of a substage is what holds a mirror in order to see what is on the slide of a microscope.
- any subdivision or part of a stage
- the part of a microscope located below the stage to which a mirror, light, etc. can be attached
The part of a microscope located below the stage on which attachments are held in place.