The way that a software application behaves based on assumption that a designer or developer made that was never validated by actual humans that have to use the application.
It's great assumptionality that you only 'need' four items in the recently used file list.
Software which performs actions that it assumes is OK with the user. An example of AssumptionWare would be a program that installs into a directory with no option for the user to specify a different one. Another example would be a program that writes log files with no
option to disable.
An assumptioneer is someone who works in a field very similar to that of an engineer but they do not have tons and tons of accurate data available to make decisions so they have to make lots of assumptions, hence this makes them an assumptioneer - doing assumptioneering work.
Project Manager - How is the work progressing on the facility design?
Design Manager - Jon has been struggling with a lack of data but as we all know he is a great assumptioneer
Project Manager - ok as long as we clearly document all our assumptions in a concept document should be fine for now